Chapter 7

Specimens examined.—Total 58, distributed as follows:Arizona:Graham County: 11/2mi. SW Ft. Grant, Graham Mts., 1[39];Pima County: 11/2mi. ENE Greaterville, Thurber Ranch, 2[39];Santa Cruz County: Patagonia, 3[39];Cochise County:9 mi. W Hereford, 10[43]; type locality, 2[43](including the type);5 mi. W Hereford, 5[43]; 91/2mi. W New Mexico State Line, 51/2mi. N Mexican border, 20[42];3 mi. E, 1 mi. N Chiricahua, 1[42].New Mexico:Hidalgo County: 18 mi. S, 2 mi. W Animas, 2;22 mi. S, 2 mi. W Rodeo, 6000 ft., 1[40];22 mi. S, 2 mi. E Rodeo, 6000 ft., 3[40]; 251/2mi. S Animas, 6200 ft. (in Big Bill Canyon), 1[40].Chihuahua:51/2mi. N, 2 mi. W San Francisco, 5100 ft., 1;21/2mi. N, 3 mi. W San Francisco, 5200 ft., 1; 11/2mi. N San Francisco, 5100 ft., 4; Casas Grandes, 4300 ft., 1[41].Marginal records>—Arizona: 11/2mi. SW Ft. Grant, Graham Mts.New Mexico: 18 mi. S, 2 mi. W Animas; 251/2mi. S Animas (in Big Bill Canyon).Chihuahua: 11/2mi. N San Francisco; Casas Grandes.Arizona: Patagonia; 11/2mi. ENE Greaterville, Thurber Ranch.[39]University of Illinois, Museum of Natural History.[40]University of New Mexico.[41]U. S. Nat. Museum (Biol. Surv. Coll.).[42]University of Arizona.[43]Univ. Michigan, Museum of Zoology.Baiomys taylori canutus, new subspeciesPeromyscus taylori paulus, Osgood, N. Amer. Fauna, 28:255, April 17, 1909 (part).Peromyscus musculus[musculus], Osgood, N. Amer. Fauna, 28:256, April 17, 1909 (part).Baiomys taylori paulus, Miller, Bull. U. S. Nat. Mus., 79:137, December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924 (part); Burt, Miscl. Publ., Mus. Zool., Univ. Michigan, 39:54, February 14, 1938; Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus. Zool., Univ. Michigan, 565:13, March 31, 1955; Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 (part).Baiomys musculus musculus, Goldman, Smith. Miscl. Coll., 115:336, July 31, 1951 (part).Type.—Adult male, skin and skull; No. 62075, University of Kansas, Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of México; obtained on June 14, 1954, by A. A. Alcorn, original number 1754.Range.—Central Nayarit northward through western Sinaloa, to as far north as south-central Sonora, seeFigure 11. Zonal range: Lower arid tropical, closely approximating the Sinaloan Biotic Province of Goldman and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet), Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.Diagnosis.—Dorsal ground color Buffy Brown (some specimens near Olive Brown); proximal fourth of individual guard hairs of dorsum black-tipped, distal three-fourths dark grayish; dorsal underfur black-tipped having subterminal band of Buffy Brown; hair around eyes buffy to base; belly Pallid Neutral Gray with overtones of buff; individual hairs in region of chin whitish-gray to bases; vibrissae blackish to bases except ventralmost, those being white to base; tail Dark Olive above, slightly paler below. Average and extreme external measurements of 13 adults from 15 mi. N Rosario, Chelé, Sinaloa, 300 ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4 (38-49); length of body, 66.2 (58-75); length of hind foot, 11.2 (10-12). Average and extreme cranial measurements of 19 adults from the same place are as follows: occipitonasal length, 18.2 (17.7-18.9); zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3); least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina, 3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8 (1.6-2.0); for photographs of skull, seePlate 2c, andPlate 4d.Comparisons.—FromB. t. ater,B. t. canutusdiffers in: dorsum slightly grayer; belly whitish to pale-gray with only faint tones of buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet flesh-colored to grayish above instead of whitish to flesh-colored; tail paler above, less hairy, scales more evident; interparietal relatively larger from anteriormost to posteriormost points; incisive foramina tapering less abruptly posteriorly, not constricted towards midline; over-all size of body and cranium somewhat larger.FromB. t. paulus,B. t. canutusdiffers in: dorsum grayish-brown rather than fawn-colored (not differing appreciably from extremes of darker brown specimens ofpaulus); forefeet and hind feet flesh-colored to grayish above[Pg 644]rather than white above; tail less hairy, unicolored to faintly bicolored rather than distinctly bicolored; braincase slightly larger; alveolar length of maxillary tooth-row slightly less.FromB. t. analogous,B. t. canutusdiffers in: dorsum paler, less of dark brown hues; belly paler; forefeet and hind feet slightly paler, less sooty above; tail less hairy, paler and having scales evident; jugal of zygoma extending ventrally to a point immediately above, instead of below, level of alveolus of upper molars; nasals more nearly truncate anteriorly; infraorbital foramina less deeply notched toward midline of skull; body and skull averaging smaller throughout.FromB. t. allex,B. t. canutusdiffers in: dorsal ground color grayish rather than fawn color having grayish overtones; underfur on dorsum darker gray; dorsal surface of forefeet and hind feet flesh-colored to grayish rather than flesh-colored; incisive foramina tapering to a point posteriorly rather than rounded posteriorly; interparietal relatively smaller; body and skull averaging larger throughout.Remarks.—Burt (1938:54) reluctantly assigned specimens from Ciudad Obregón toB. t. paulus, probably being influenced by the resemblance in size. He suggested that, perhaps, a distinct subspecies occurs in the State of Sonora. Study of larger series of specimens than were available to Burt reveals that populations of pygmy mice inhabiting the northwest coastal plains of México are indeed distinct.The darkest of the material assigned tocanutusis from Nayarit (for specific localities see specimens examined). According to Tamayo (1949:Carta de Suelos), color of soil changes from chestnut in northern Sinaloa to black in southern Sinaloa and northern Nayarit. There seems, therefore, to be a close correlation between color of pelage and color of soil in this area. In Nayarit, particularly in the central and southern parts, the mice are intermediate in color between the paler, grayer population to the north and the more brownish samples, representative ofallexto the south. The coastal vegetation changes from the arid tropical thorn forests of the north and central parts of Sinaloa to a savannah in Nayarit, thence to a tropical deciduous forest farther south (see Leopold, 1950:508).In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW Rosa Morada are intermediate between the larger, grayercanutusand the smaller, light-brownishallex. In size of cranium, these specimens are more nearly likecanutus, and are referred to that subspecies. Mice from the western coastal plain are relatively homogeneous as regards size of body and skull, except that those from 13.5 mi. S Acaponéta, Nayarit, average somewhat larger.B. t. canutus, likeB. t. subater, is predominantly a lowland or coastal subspecies. The pallor of the former, that lives on generally paler soils, presumably is of adaptive value.Pygmy mice are seemingly rare in the northern part of the range of this subspecies. J. Raymond Alcorn and Albert Alcorn were successful in collecting only two specimens from the type locality after three successive nights of trapping with 100 traps set each night. Only six specimens are known from Sonora. These were obtained in the irrigated regions of Ciudad, Obregón, and Navajoa. Charles Sibley obtained one specimen 10.6 mi. SE Ciudad Obregón in a "maguey field." I obtained one specimen 1 mi. NNW Navajoa in a sparse grassway, 20 feet wide, bordering an open sewer, which coursed northward into the Río Mayo. Irrigated wheat fields bordered the grassway and ditch.Specimens examined.—Total 70 all from the Republic of México and distributed as follows:Sonora: [Ciudad] Obregón, 4[44]; 10.6 mi. SE [Ciudad] Obregón, 1[45]; 1 mi. NNW Navajoa, 1.Sinaloa: type locality, 2 (including the type); Culiacán, 175 ft., 2[46]; Mazatlán, 1[48];15 mi. N Rosario, Chelé, 300 ft., 35[47]; Rosario, 3[46]; Escuinapa, 5[48];Railroad Station Escuinapa, 43 ft., 2[45].Nayarit: Acaponéta, 4[46];13.5 mi. S Acaponéta Junction, 6[49]; 2 mi. SW Rosa Morada, 2;2 mi. WNW Tepic, 3200 ft., 1; 3 mi. SE Tepic, 1.Marginal records.—Sonora[Ciudad] Obregón.Sinaloa: type locality; Escuinapa.Nayarit: Acaponéta; 3 mi. SE Tepic.Sinaloa: Mazatlán.[44]Coll. Univ. California, Los Angeles.[45]Univ. California, Mus. Vert. Zoology.[46]U. S. Nat. Museum (Biol. Surv. Coll.).[47]Univ. Michigan, Museum of Zoology.[48]American Museum of Natural History.[49]Univ. Illinois, Mus. Nat. History.Baiomys taylori fuliginatus, new subspeciesBaiomys taylori taylori, Dalquest, Louisiana State Univ. Studies (Biol. Sci. Ser.) 1:155, December 28, 1953 (part).Baiomys taylori taylori, Booth, Walla Walla Publs. Dept. Biol. Sci., 20:15, July 10, 1957 (part).Type.—Adult male, skin and skull; No. 36765, University of Kansas, Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maíz, 4000 ft., San Luis Potosí, Republic of México; obtained on January 17, 1950, by J. R. Alcorn, original number 10400.Range.—Occurs in the Sierra Madre Oriental of the northeastern third of San Luis Potosí. Zonal range: Upper Tropical (see Dalquest, 1953:10); approximates a part of the Sierra Madre Oriental Biotic Province of Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up to 4000 feet at Ciudad del Maíz.Diagnosis.—Size large for the species; ground color of dorsum Chaetura Drab; individual guard hairs of dorsum black to base, distal fourth of hairs of underfur in posterior half of dorsum tipped with grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior region of dorsum, posterior to ears, distal third of hairs grayish-brown and proximal two-thirds Dark Neutral Gray to base; sides slightly paler than dorsum; ground color of belly Neutral Gray, individual hairs of belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral Gray to Dark Neutral Gray; tips of individual hairs of face Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral vibrissae black to base; forefeet and hind feet sooty above and below, thigh bearing[Pg 646]some white-tipped hairs; tail near Chaetura Drab above, Pale Neutral Gray below; anterior part of jugal projecting slightly ventrally and forming small protuberance at point of articulation with maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal. In most cranial measurements averaging as large asB. t. analogous. Average and extreme measurements of the type and three additional paratypes, all adults, are: total length, 105.5 (101-109); length of tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot, 14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length, 18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length, 6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4); breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of skull, seePlate 2d, andPlate 4e.Comparisons.—FromB. t. taylori,B. t. fuliginatusdiffers in: dorsum slightly darker than in darkesttaylori; tail densely haired, bicolored rather than unicolored; belly sooty to grayish rather than grayish to whitish; forefeet and hind feet sooty to grayish rather than flesh-colored; incisive foramina less bowed laterally, more nearly straight; interparietal compressed anteroposteriorly, less diamond-shaped.FromB. t. paulus,B. t. fuliginatusdiffers in: dorsum dusky to blackish rather than fawn color; belly sooty to grayish rather than buffy to whitish-gray; forefeet and hind feet sooty to grayish rather than whitish; zygoma more nearly forming a right angle with rostrum or skull, less tapered anteriorly; anterior part of jugal possessing ventral projection; jugal extending nearly to lacrimal on posterior surface of maxillary part of zygoma.FromB. t. analogous,B. t. fuliginatusdiffers in: mid-dorsal region blacker, less brownish; tail distinctly bicolored rather than unicolored to faintly bicolored; incisive foramina not constricted medially; presphenoid broader (at narrowest point); jugal differs much the same as it does frompaulus; nasals anteriorly truncate instead of rounded.Remarks.—Dalquest (1953:155-157) and Booth (1957:15) assigned all of the pygmy mice that they examined from the state of San Luis Potosí toB. t. taylori. Examination of all of the material that was available to Dalquest, plus additional specimens at the University of Kansas Museum of Natural History, reveals that there are three subspecies in San Luis Potosí.B. t. taylorioccurs in the eastern part of the State at lower altitudes;B. t. analogousoccurs to the southeast at higher altitudes;B. t. fuliginatusoccurs in the northeastern part of the State in the Sierra Madre Oriental.Specimens obtained from Ebano, Pujal, and Tamuín, representative ofB. t. taylori, are much paler on the belly and on the ventral surface of the forefeet and hind feet than are specimens from Ciudad del Maíz, representative ofB. t. fuliginatus. The tail inB. t. tayloriis nearly unicolored and less hairy than in the paratypical series offuliginatus. Specimens from 4 km. NE Ciudad Valles are nearly intermediate in color of the belly, dorsum, forefeet and hindfeet, and tail, between the palest mice from the coastal plain and the darker mice in the mountains of the northeastern part of the State (specimens from El Salto average paler, however, than the type and paratypes). These specimens seem to be intergrades betweenB. t. taylorito the east on the coastal plain andfuliginatusto the northwest in the mountains. It seems best to refer the mice from 4 km. N Ciudad Valles toB. t. taylorion the basis of the average of external and cranial characters. Specimens from 6 mi. SW San Gerónimo, Coahuila, also referred toB. t. taylori, resemble in color the mice from 4 km. N Ciudad Valles. When more specimens are obtained from the front range of the Sierra Madre Oriental, at lower altitudes, the manner in which these two subspecies intergrade with one another will be better understood. At present, populations from higher altitudes in the mountains seem to represent a dark subspecies; populations from the coastal plain represent a pale subspecies, and those from the lower slopes and high valleys seemingly are intergrades.B. t. fuliginatusoccurs in a somewhat limited strip of chernozem soil (or suelos negros of Tamayo, 1949: Carta de Suelos). The populations occurring at lower altitudes on the coastal plain are on generally paler soils.Specimens examined.—Total 39, all from the Republic of México, as follows:San Luis Potosí: El Salto, 24 Mus. Nat. Hist., Louisiana State Univ., 7 Amer. Mus. Nat. Hist.; type locality, 8 (including the type).Marginal records.—See specimens examined.Baiomys taylori paulus(J. A. Allen)Peromyscus paulus, J. A. Allen, Bull. Amer. Mus. Nat. Hist., 19:598, November 12, 1903; Elliot, Field Columb. Mus. Publ., 105(6): 136, July 1, 1905.Baiomys taylori paulus, Miller, Bull. U. S. Nat. Mus., 79:137, December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924 (part); Ellerman, The Families and Genera of Living Rodents, 2:402, March 21, 1941 (part); Goldman, Smith, Miscl. Coll., 115:373, July 31, 1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist., 26:367, December 15, 1952; Goodwin, Bull. Amer. Mus. Nat. Hist., 102:318, August 31, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955 (part); Packard, Proc. Biol. Soc. Washington, 71:17, April 11, 1958; Packard, Jour. Mamm., 40:146, February 20, 1959; Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 (part).[Peromyscus]paulus, Elliot, Field Columb, Mus. Publ., 95(4):136, July 15, 1904.Peromyscus taylori paulus, Osgood, N. Amer. Fauna, 28:255, April 17, 1909 (part).Peromyscus musculus[musculus], Osgood, N. Amer. Fauna, 28:256, April 17, 1909 (part).Baiomys taylori[=paulus], Twente and Baker, Jour. Mamm., 32:121, February 15, 1951.Baiomys musculus musculus, Goldman, Smith. Miscl. Coll., 115:336, July 31, 1951 (part).Baiomys taylori allex, Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 (part).Type.—Adult male, skin and skull; No. 21165, American Museum of Natural History; Río Sestín, Durango, Republic of México; obtained on April 15, 1903, by J. H. Batty, original number 455.Range.—Central Chihuahua south through Durango (west to eastern edge of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence west into northern and northwestern Jalisco, seeFigure 11. Zonal range: Lower Sonoran, approximately the Chihuahua Desert Biotic Province of Goldman and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila, Jalisco, up to 6700 feet 2 mi. W Miñaca, Chihuahua.Diagnosis.—Size medium to small for the species; dorsum Buffy Brown to fawn color; dorsal ground color of unworn pelage of adults varying from Buffy Brown in darkest series (especially those from higher altitudes) to Avellaneous with grayish overtones in palest series; worn pelage in mid-dorsal region of adults fawn to grayish; terminal parts of individual hairs buffy, gray basally; guard hairs on dorsum black-tipped, grayish basally; belly Light Gull Gray, distal half of hairs white, proximal half Neutral Gray; hairs in region of throat and chin white to base (some specimens with faint buffy overtones); forefeet dusky below, whitish above; hind feet whitish above, ventral surface whitish to dusky; dorsal and lateral vibrissae black, other vibrissae white. Average and extreme measurements of six adults from the type locality are as follows: total length, 109 (106-117); length of tail, 44.5 (43-48); length of body, 63 (57-69); length of hind foot, 13.1 (12.7-14.0); occipitonasal length, 17.5 (17.4-18.0); zygomatic breadth, 9.3 (9.1-9.5); postpalatal length, 6.6 (6.2-6.9); least interorbital breadth, 3.5 (3.4-3.6); length of incisive foramina, 3.8 (3.6-4.1); length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6 (8.5-8.8); depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of the skull, seePlate 2eandPlate 4f.Comparisons.—For comparisons withB. t. allex,B. t. canutus,B. t. ater, andB. t. taylori, see accounts of those subspecies. FromB. t. analogous,B. t. paulusdiffers as follows: dorsal color paler having more reddish-brown than blackish-brown tones; venter whitish to buffy, instead of gray to light-gray; tail bicolored (not unicolored), usually having more hairs; hind feet white (not sooty) above. Cranially,B. t. paulusdiffers fromB. t. analogousin: skull slightly smaller in all dimensions; maxillary part of zygoma narrowing and forming oblique angle rather than a near right angle with rostrum; anterior incisive foramina constricted posteriorly; tips of nasals truncate (less rounded).Remarks.—J. A. Allen (1903:599) correctly pointed out that young specimens, in first pelage, were gray brown; young adults were darker and more varied with some blackish; adults and old adults were buffy to grayish. The change in color of pelage with increasing age is more pronounced inpaulusthan in other subspecies ofB. taylori. Of two males collected on April 12, 1949, one, an adult, is buffy brown, and the other, an old adult with worn pelage, is grayish-brown. In mice in the earlier stages of adulthood,underfur of the dorsum is buffy at the tips and gray basally. With increased wear, the buffy tip is lost. Consequently, mice in the later stages of adulthood are grayish.B. t. paulusintergrades withaterto the north in Chihuahua (see account of that subspecies), withanalogousto the south in Jalisco, and withallex(see account of that subspecies) to the southwest in Nayarit and Jalisco. The zone of intergradation betweenpaulusandanalogousin Jalisco approximately borders the Río Grande de Santiago from the western part of the State to the northwest shore of Lago de Chapala. Nineteen specimens from 2 mi. WNW Lagos de Moreno in northwest Jalisco seem to be intermediate betweenpaulusandanalogousin color, averaging slightly grayer than typicalpaulus. The series of 19 is referable topauluson the basis of cranial characters.A series of 34 specimens from 3 mi. W La Venta, Jalisco (referable topaulus), is indistinguishable in color of pelage from two series ofpaulusfrom 5 mi. N Durango, and from 8 mi. NE of Durango, except that the antiplantar surfaces of the hind feet are sooty as inanalogous. Seemingly, features of color mentioned above as diagnostic of the two subspecies are either present or absent and there is no tendency toward intermediacy in color in the population from 3 mi. W La Venta.The Río Grande de Santiago may have acted in the past as a physical barrier reducing gene flow betweenallexandpaulusand in separating completely the two populations for limited periods.Specimens examined.—Total 176, all from the Republic of México and distributed as follows:Chihuahua: Rancho Sanignacio, 4 mi. S, 1 mi. W Santo Tomás, 1; El Rosario, 6700 ft., 1; 2 mi. W Miñaca, 6900 ft., 11; Balleza, 1[50].Durango: Rosario, 1[51]; type locality, 14[51](including the type);San Gabriel, 2[51];Rancho Santuario, 2[51]; 1 mi. N Chorro, 6450 ft., 1;8 mi. NE Durango, 6200 ft., 2; 5 mi. N Durango, 6400 ft., 2.Zacatecas: Valparaíso, 6500 ft., 10[50].Aguascalientes:18 mi. W, 2 mi. S Aguascalientes, 6000 ft., 1; 16 mi. S Aguascalientes, 5[52].Jalisco: 1 mi. NE Villa Hidalgo, 6500 ft., 1; 2 mi. WNW Lagos de Moreno, 6370 ft., 19;2 mi. ESE Tequila, 4000 ft., 11;3 mi. W La Venta, 33, 1[53];12 mi. W Guadalajara, 3[54];Atemajac, 12[50]; 4 mi. W Guadalajara, 5100 ft., 3;2 mi. N,1/2mi. W Guadalajara, 11; 2 mi. NW Magdalena, 4500 ft., 7[50];1 mi. N Tala, 4400 ft., 3; 3 mi. W Tala, 4300 ft., 18.Marginal records.—Chihuahua: Rancho Sanignacio, 4 mi. S, 1 mi. W Santo Tomás; El Rosario; Balleza.Durango: Rosario, 6700 ft.; 1 mi. E Zarca (Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft.Zacatecas: Valparaíso, 6500 ft.Aguascalientes: 1 mi. N Chicalote (Blossom and Burt, 1942:4).Jalisco: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W Guadalajara, 5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500 ft.Durango: 5 mi. N Durango, 6400 ft.; type locality.Chihuahua: 2 mi. W Miñaca, 6900 ft.[50]United States National Museum (Biol. Surv. Collections).[51]American Museum of Natural History.[52]Univ. Illinois, Mus. Nat. History.[53]The Museum, Michigan State Univ.[54]Univ. Michigan, Museum of Zoology.Baiomys taylori subater(V. Bailey)Peromyscus taylori subater, V. Bailey, N. Amer. Fauna, 25:102, October 24, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:139, January 15, 1909; Osgood, N. Amer. Fauna, 28:255, April 17, 1909; Elliot, Check-List Mamm. N. Amer. Continent, West Indies and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist, p. 44, January 8, 1917.Baiomys taylori subater, Miller, Bull. U. S. Nat. Mus., 79:136, December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924; Anthony, Field Book of North American Mammals, p. 348, 1928; Baker, Jour. Mamm., 21:223, May 14, 1940; Ellerman, The Families and Genera of Living Rodents, 2:402, March 21, 1941; Blair, Jour. Mamm., 22:378, November 14, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942; Blair, Jour. Mamm., 23:196, May 14, 1942; Blair and Blossom, Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955; Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959.Baiomys taylori[=subater], Taylor and Davis, Texas Game, Fish and Oyster Comm. Bull., 27:56, August, 1947 (part).Type.—Subadult female, skin and skull; No. 32616/44539 U. S. Nat. Mus. (Biol. Surv. Coll.); Bernard Creek, near Columbia, Brazoria County, Texas; obtained on February 25, 1892, by W. Lloyd, original number 1122.Range.—Southeastern Texas, north of Matagorda Bay west to Lavaca County, north to Brazos and Walker counties thence east to Jefferson County, seeFigure 11. Occurs from near sea level in Brazoria and Galveston counties, up to 500 feet in western part of range. Zonal range: Humid division of lower Austral (the western part of the Austroriparian Biotic Province of Dice, 1943:18-21).Diagnosis.—Size medium to large for the species; mid-dorsal region Clove Brown (sooty in freshly captured specimens); some parts of mid-dorsal region all blackish; individual guard hairs of dorsum black-tipped, Deep Neutral Gray basally; underfur black-tipped with subterminal band of light buff, Neutral Gray at base; belly grayish-white, laterally Isabella Color; distal three-fourths of hairs in region of throat and chin white, proximal fourth light gray; in median region of belly distal half of individual hairs white, proximal half dark gray; vibrissae in most specimens black to base. Average and extreme cranial measurements of six adults from 7 mi. S La Belle are as follows: occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6 (9.1-9.9); postpalatal length, 6.8 (6.2-7.2); least interorbital breadth, 3.7 (3.4-3.9); length of incisive foramina, 4.0 (3.6-4.2); length of rostrum, 6.5 (6.1-6.8); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.7 (6.6-6.8); alveolar length of maxillary tooth-row, 3.1 (2.9-3.2). Average and extreme external measurements of four adults from Richmond are as follows: total length, 111.5 (108-118); length of tail vertebrae, 43.5 (41-47); length of body, 68 (67-71); length of hind foot, 14 (13-15); for photographs of the skull, seePlate 2f, andPlate 4g.Comparisons.—BecauseB. t. subaterintergrades only withB. t. taylorito the south and west,subateris compared only withtaylori. Young adults of both subspecies in unworn pelage show best the colors that differentiate the two subspecies. Old adults ofsubaterin worn pelage appear grayish, resemblingtaylori, and at that age, only certain cranial characters are of taxonomic use. Cranially,subaterdiffers fromtayloriin: presphenoid not shaped like an hour-glass; parapterygoid processes thicker medially; interparietal diamond-shaped instead of elongated and compressed. Skull slightly larger in most measurements.PLATE 1Photographs of skulls in dorsal view ofBaiomys. × 2.a.B. m. brunneus, ♀ ad., 10834, AMNH, Jalapa, Veracruz.b.B. m. grisescens, ♀ ad., 257080, USNM, Comayabuela, Honduras.c.B. m. handleyi, ♀ ad., 275597, USNM, Sacapulas, Guatemala.d.B. m. infernatis, ♀ ad., 91499, MZUM, Teotitlán, Oaxaca.e.B. m. musculus, ♀ ad., 45462, USNM, Colima, Colima.f.B. m. nigrescens, ♂ ad., 76834, USNM, Comitán, Chiapas.g.B. m. pallidus, ♀ ad., 4802, Texas A & M, Axochiapán, Morelos.h.B. m. pullus, ♀ ad., 71608, KU, 8 mi. S Condega, Nicaragua.i.B. t. allex, ♀ ad., 45453, USNM, Colima, Colima.PLATE 2Photographs of skulls (a-g) in dorsal view ofBaiomys. × 2.a.B. t. analogous, ♀ ad., 120265, USNM, Zamora, Michoacán.b.B. t. ater, ♀ ad., 15056, UI, 11/2mi. ENE Greaterville, Arizona.c.B. t. canutus, ♀ ad., 62076, KU, 1 mi. S Pericos, Sinaloa.d.B. t. fuliginatus, ♀ ad., 36771, KU, type locality.e.B. t. paulus, ♀ ad., 40032, KU, 18 mi. W, 2 mi. S Aguascalientes.f.B. t. subater, ♀ ad., 44543, USNM, type locality.g.B. t. taylori, ♀ ad., 57944, KU, 5 mi. E San Antonio, Texas.h.Photo. of captive ♂B. t. taylori, 25 mi. E Austin, Texas. × 1.PLATE 3Photographs of skulls in ventral view ofBaiomys. × 2.a.B. m. brunneus, ♀ ad., 10834, AMNH, Jalapa, Veracruz.b.B. m. grisescens, ♀ ad., 257080, USNM, Comayabuela, Honduras.c.B. m. handleyi, ♀ ad., 275597, USNM, Sacapulas, Guatemala.d.B. m. infernatis, ♀ ad., 91499, MZUM, Teotitlán, Oaxaca.e.B. m. musculus, ♀ ad., 45462, USNM, Colima, Colima.f.B. m. nigrescens, ♂ ad., 76834, USNM, Comitán, Chiapas.g.B. m. pallidus, ♀ ad., 4802, Texas A & M, Axochiapán, Morelos.h.B. m. pullus, ♀ ad., 71608, KU, 8 mi. S Condega, Nicaragua.PLATE 4Photographs of skulls in ventral view ofBaiomys. × 2.a.B. t. allex, ♀ ad., 45453, USNM, Colima, Colima.b.B. t. analogous, ♀ ad., 120265, USNM, Zamora, Michoacán.c.B. t. ater, ♀ ad., 15056, UI, 1 mi. ENE Greaterville, Arizona.d.B. t. canutus, ♀ ad., 62076, KU, 1 mi. S Pericos, Sinaloae.B. t. fuliginatus, ♀ ad., 36771, KU, type locality.f.B. t. paulus, ♀ ad., 40032, KU, 18 mi. W, 2 mi. S Aguascalientes.g.B. t. subater, ♀ ad., 44543, USNM, type locality.h.B. t. taylori, ♀ ad., 57944, KU, 5 mi. E San Antonio, Texas.Remarks.—This subspecies retains its chief diagnostic character, blackish mid-dorsal region, throughout nearly all parts of its range. Specimens from the general area of Matagorda Bay and Lavaca County grade intotayloriin characters of color and crania. The Colorado and Brazos rivers seemingly serve as barriers reducing gene flow betweentayloriandsubater. These rivers may well have been important factors in the origin and the limitation of these two seemingly closely-related subspecies.Baiomys taylori subateris not differentiated in color of pelage and characters of crania fromB. t. taylorito the same degree thatB. t. paulusis differentiated fromB. t. analogous, or thatB. t. tayloriis differentiated from several of the other subspecies ofBaiomys taylori.B. t. subaterprobably is a more recent occupant of the area in which it now lives than is the case with any other one of the subspecies oftaylori. Sufficient time probably has not elapsed to allow for formation of more distinctive phenotypic patterns.Specimens examined.—Total 65, all fromTexasand distributed as follows:Brazos County:1/2mi. NW College Station, 1[55];3 mi. W College Station,1 mi. W Easterwood Airport, 1[55];College Station, 1[55].Walker County: Huntsville, 1[55].Hardin County: Sour Lake, 1[57].Jefferson County: 7 mi. S Labelle, 10.Harris County: 6 mi. NE Crosby, 1[56].Colorado County:10 mi. N Eagle Lake, 1[55];9 mi. N Eagle Lake, 1[55]; 2 mi. W Eagle Lake, 1;Eagle Lake, 1[55], 5.Fort Bend County: Richmond, 4[57].Galveston County:Texas City, 6[58]; Virginia Point, 1[57].Brazoria County:Austin Bayou near Alvin, 2[57]; 14 mi. SSE Alvin, 2[59]; type locality, 7[57](including the type).Lavaca County: 4 mi. W Hallettsville, 1[55];1 mi. SW Hallettsville, 3[55];13.7 mi. SW Hallettsville, 2[55]; 4 mi. NE Yoakum, 11.Marginal records.—Texas: Huntsville; Sour Lake; 7 mi. S La Belle; Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi. W Hallettsville;1/2mi. NW College Station.

Marginal records>—Arizona: 11/2mi. SW Ft. Grant, Graham Mts.New Mexico: 18 mi. S, 2 mi. W Animas; 251/2mi. S Animas (in Big Bill Canyon).Chihuahua: 11/2mi. N San Francisco; Casas Grandes.Arizona: Patagonia; 11/2mi. ENE Greaterville, Thurber Ranch.

[39]University of Illinois, Museum of Natural History.

[40]University of New Mexico.

[41]U. S. Nat. Museum (Biol. Surv. Coll.).

[42]University of Arizona.

[43]Univ. Michigan, Museum of Zoology.

Baiomys taylori canutus, new subspecies

Peromyscus taylori paulus, Osgood, N. Amer. Fauna, 28:255, April 17, 1909 (part).

Peromyscus musculus[musculus], Osgood, N. Amer. Fauna, 28:256, April 17, 1909 (part).

Baiomys taylori paulus, Miller, Bull. U. S. Nat. Mus., 79:137, December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924 (part); Burt, Miscl. Publ., Mus. Zool., Univ. Michigan, 39:54, February 14, 1938; Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus. Zool., Univ. Michigan, 565:13, March 31, 1955; Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 (part).

Baiomys musculus musculus, Goldman, Smith. Miscl. Coll., 115:336, July 31, 1951 (part).

Type.—Adult male, skin and skull; No. 62075, University of Kansas, Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of México; obtained on June 14, 1954, by A. A. Alcorn, original number 1754.Range.—Central Nayarit northward through western Sinaloa, to as far north as south-central Sonora, seeFigure 11. Zonal range: Lower arid tropical, closely approximating the Sinaloan Biotic Province of Goldman and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet), Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.Diagnosis.—Dorsal ground color Buffy Brown (some specimens near Olive Brown); proximal fourth of individual guard hairs of dorsum black-tipped, distal three-fourths dark grayish; dorsal underfur black-tipped having subterminal band of Buffy Brown; hair around eyes buffy to base; belly Pallid Neutral Gray with overtones of buff; individual hairs in region of chin whitish-gray to bases; vibrissae blackish to bases except ventralmost, those being white to base; tail Dark Olive above, slightly paler below. Average and extreme external measurements of 13 adults from 15 mi. N Rosario, Chelé, Sinaloa, 300 ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4 (38-49); length of body, 66.2 (58-75); length of hind foot, 11.2 (10-12). Average and extreme cranial measurements of 19 adults from the same place are as follows: occipitonasal length, 18.2 (17.7-18.9); zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3); least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina, 3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8 (1.6-2.0); for photographs of skull, seePlate 2c, andPlate 4d.Comparisons.—FromB. t. ater,B. t. canutusdiffers in: dorsum slightly grayer; belly whitish to pale-gray with only faint tones of buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet flesh-colored to grayish above instead of whitish to flesh-colored; tail paler above, less hairy, scales more evident; interparietal relatively larger from anteriormost to posteriormost points; incisive foramina tapering less abruptly posteriorly, not constricted towards midline; over-all size of body and cranium somewhat larger.FromB. t. paulus,B. t. canutusdiffers in: dorsum grayish-brown rather than fawn-colored (not differing appreciably from extremes of darker brown specimens ofpaulus); forefeet and hind feet flesh-colored to grayish above[Pg 644]rather than white above; tail less hairy, unicolored to faintly bicolored rather than distinctly bicolored; braincase slightly larger; alveolar length of maxillary tooth-row slightly less.FromB. t. analogous,B. t. canutusdiffers in: dorsum paler, less of dark brown hues; belly paler; forefeet and hind feet slightly paler, less sooty above; tail less hairy, paler and having scales evident; jugal of zygoma extending ventrally to a point immediately above, instead of below, level of alveolus of upper molars; nasals more nearly truncate anteriorly; infraorbital foramina less deeply notched toward midline of skull; body and skull averaging smaller throughout.FromB. t. allex,B. t. canutusdiffers in: dorsal ground color grayish rather than fawn color having grayish overtones; underfur on dorsum darker gray; dorsal surface of forefeet and hind feet flesh-colored to grayish rather than flesh-colored; incisive foramina tapering to a point posteriorly rather than rounded posteriorly; interparietal relatively smaller; body and skull averaging larger throughout.

Range.—Central Nayarit northward through western Sinaloa, to as far north as south-central Sonora, seeFigure 11. Zonal range: Lower arid tropical, closely approximating the Sinaloan Biotic Province of Goldman and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet), Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.

Diagnosis.—Dorsal ground color Buffy Brown (some specimens near Olive Brown); proximal fourth of individual guard hairs of dorsum black-tipped, distal three-fourths dark grayish; dorsal underfur black-tipped having subterminal band of Buffy Brown; hair around eyes buffy to base; belly Pallid Neutral Gray with overtones of buff; individual hairs in region of chin whitish-gray to bases; vibrissae blackish to bases except ventralmost, those being white to base; tail Dark Olive above, slightly paler below. Average and extreme external measurements of 13 adults from 15 mi. N Rosario, Chelé, Sinaloa, 300 ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4 (38-49); length of body, 66.2 (58-75); length of hind foot, 11.2 (10-12). Average and extreme cranial measurements of 19 adults from the same place are as follows: occipitonasal length, 18.2 (17.7-18.9); zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3); least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina, 3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8 (1.6-2.0); for photographs of skull, seePlate 2c, andPlate 4d.

Comparisons.—FromB. t. ater,B. t. canutusdiffers in: dorsum slightly grayer; belly whitish to pale-gray with only faint tones of buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet flesh-colored to grayish above instead of whitish to flesh-colored; tail paler above, less hairy, scales more evident; interparietal relatively larger from anteriormost to posteriormost points; incisive foramina tapering less abruptly posteriorly, not constricted towards midline; over-all size of body and cranium somewhat larger.

FromB. t. paulus,B. t. canutusdiffers in: dorsum grayish-brown rather than fawn-colored (not differing appreciably from extremes of darker brown specimens ofpaulus); forefeet and hind feet flesh-colored to grayish above[Pg 644]rather than white above; tail less hairy, unicolored to faintly bicolored rather than distinctly bicolored; braincase slightly larger; alveolar length of maxillary tooth-row slightly less.

FromB. t. analogous,B. t. canutusdiffers in: dorsum paler, less of dark brown hues; belly paler; forefeet and hind feet slightly paler, less sooty above; tail less hairy, paler and having scales evident; jugal of zygoma extending ventrally to a point immediately above, instead of below, level of alveolus of upper molars; nasals more nearly truncate anteriorly; infraorbital foramina less deeply notched toward midline of skull; body and skull averaging smaller throughout.

FromB. t. allex,B. t. canutusdiffers in: dorsal ground color grayish rather than fawn color having grayish overtones; underfur on dorsum darker gray; dorsal surface of forefeet and hind feet flesh-colored to grayish rather than flesh-colored; incisive foramina tapering to a point posteriorly rather than rounded posteriorly; interparietal relatively smaller; body and skull averaging larger throughout.

Remarks.—Burt (1938:54) reluctantly assigned specimens from Ciudad Obregón toB. t. paulus, probably being influenced by the resemblance in size. He suggested that, perhaps, a distinct subspecies occurs in the State of Sonora. Study of larger series of specimens than were available to Burt reveals that populations of pygmy mice inhabiting the northwest coastal plains of México are indeed distinct.

The darkest of the material assigned tocanutusis from Nayarit (for specific localities see specimens examined). According to Tamayo (1949:Carta de Suelos), color of soil changes from chestnut in northern Sinaloa to black in southern Sinaloa and northern Nayarit. There seems, therefore, to be a close correlation between color of pelage and color of soil in this area. In Nayarit, particularly in the central and southern parts, the mice are intermediate in color between the paler, grayer population to the north and the more brownish samples, representative ofallexto the south. The coastal vegetation changes from the arid tropical thorn forests of the north and central parts of Sinaloa to a savannah in Nayarit, thence to a tropical deciduous forest farther south (see Leopold, 1950:508).

In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW Rosa Morada are intermediate between the larger, grayercanutusand the smaller, light-brownishallex. In size of cranium, these specimens are more nearly likecanutus, and are referred to that subspecies. Mice from the western coastal plain are relatively homogeneous as regards size of body and skull, except that those from 13.5 mi. S Acaponéta, Nayarit, average somewhat larger.

B. t. canutus, likeB. t. subater, is predominantly a lowland or coastal subspecies. The pallor of the former, that lives on generally paler soils, presumably is of adaptive value.

Pygmy mice are seemingly rare in the northern part of the range of this subspecies. J. Raymond Alcorn and Albert Alcorn were successful in collecting only two specimens from the type locality after three successive nights of trapping with 100 traps set each night. Only six specimens are known from Sonora. These were obtained in the irrigated regions of Ciudad, Obregón, and Navajoa. Charles Sibley obtained one specimen 10.6 mi. SE Ciudad Obregón in a "maguey field." I obtained one specimen 1 mi. NNW Navajoa in a sparse grassway, 20 feet wide, bordering an open sewer, which coursed northward into the Río Mayo. Irrigated wheat fields bordered the grassway and ditch.

Specimens examined.—Total 70 all from the Republic of México and distributed as follows:Sonora: [Ciudad] Obregón, 4[44]; 10.6 mi. SE [Ciudad] Obregón, 1[45]; 1 mi. NNW Navajoa, 1.Sinaloa: type locality, 2 (including the type); Culiacán, 175 ft., 2[46]; Mazatlán, 1[48];15 mi. N Rosario, Chelé, 300 ft., 35[47]; Rosario, 3[46]; Escuinapa, 5[48];Railroad Station Escuinapa, 43 ft., 2[45].Nayarit: Acaponéta, 4[46];13.5 mi. S Acaponéta Junction, 6[49]; 2 mi. SW Rosa Morada, 2;2 mi. WNW Tepic, 3200 ft., 1; 3 mi. SE Tepic, 1.Marginal records.—Sonora[Ciudad] Obregón.Sinaloa: type locality; Escuinapa.Nayarit: Acaponéta; 3 mi. SE Tepic.Sinaloa: Mazatlán.

Marginal records.—Sonora[Ciudad] Obregón.Sinaloa: type locality; Escuinapa.Nayarit: Acaponéta; 3 mi. SE Tepic.Sinaloa: Mazatlán.

[44]Coll. Univ. California, Los Angeles.

[45]Univ. California, Mus. Vert. Zoology.

[46]U. S. Nat. Museum (Biol. Surv. Coll.).

[47]Univ. Michigan, Museum of Zoology.

[48]American Museum of Natural History.

[49]Univ. Illinois, Mus. Nat. History.

Baiomys taylori fuliginatus, new subspecies

Baiomys taylori taylori, Dalquest, Louisiana State Univ. Studies (Biol. Sci. Ser.) 1:155, December 28, 1953 (part).

Baiomys taylori taylori, Booth, Walla Walla Publs. Dept. Biol. Sci., 20:15, July 10, 1957 (part).

Type.—Adult male, skin and skull; No. 36765, University of Kansas, Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maíz, 4000 ft., San Luis Potosí, Republic of México; obtained on January 17, 1950, by J. R. Alcorn, original number 10400.Range.—Occurs in the Sierra Madre Oriental of the northeastern third of San Luis Potosí. Zonal range: Upper Tropical (see Dalquest, 1953:10); approximates a part of the Sierra Madre Oriental Biotic Province of Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up to 4000 feet at Ciudad del Maíz.Diagnosis.—Size large for the species; ground color of dorsum Chaetura Drab; individual guard hairs of dorsum black to base, distal fourth of hairs of underfur in posterior half of dorsum tipped with grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior region of dorsum, posterior to ears, distal third of hairs grayish-brown and proximal two-thirds Dark Neutral Gray to base; sides slightly paler than dorsum; ground color of belly Neutral Gray, individual hairs of belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral Gray to Dark Neutral Gray; tips of individual hairs of face Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral vibrissae black to base; forefeet and hind feet sooty above and below, thigh bearing[Pg 646]some white-tipped hairs; tail near Chaetura Drab above, Pale Neutral Gray below; anterior part of jugal projecting slightly ventrally and forming small protuberance at point of articulation with maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal. In most cranial measurements averaging as large asB. t. analogous. Average and extreme measurements of the type and three additional paratypes, all adults, are: total length, 105.5 (101-109); length of tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot, 14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length, 18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length, 6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4); breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of skull, seePlate 2d, andPlate 4e.Comparisons.—FromB. t. taylori,B. t. fuliginatusdiffers in: dorsum slightly darker than in darkesttaylori; tail densely haired, bicolored rather than unicolored; belly sooty to grayish rather than grayish to whitish; forefeet and hind feet sooty to grayish rather than flesh-colored; incisive foramina less bowed laterally, more nearly straight; interparietal compressed anteroposteriorly, less diamond-shaped.FromB. t. paulus,B. t. fuliginatusdiffers in: dorsum dusky to blackish rather than fawn color; belly sooty to grayish rather than buffy to whitish-gray; forefeet and hind feet sooty to grayish rather than whitish; zygoma more nearly forming a right angle with rostrum or skull, less tapered anteriorly; anterior part of jugal possessing ventral projection; jugal extending nearly to lacrimal on posterior surface of maxillary part of zygoma.FromB. t. analogous,B. t. fuliginatusdiffers in: mid-dorsal region blacker, less brownish; tail distinctly bicolored rather than unicolored to faintly bicolored; incisive foramina not constricted medially; presphenoid broader (at narrowest point); jugal differs much the same as it does frompaulus; nasals anteriorly truncate instead of rounded.

Range.—Occurs in the Sierra Madre Oriental of the northeastern third of San Luis Potosí. Zonal range: Upper Tropical (see Dalquest, 1953:10); approximates a part of the Sierra Madre Oriental Biotic Province of Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up to 4000 feet at Ciudad del Maíz.

Diagnosis.—Size large for the species; ground color of dorsum Chaetura Drab; individual guard hairs of dorsum black to base, distal fourth of hairs of underfur in posterior half of dorsum tipped with grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior region of dorsum, posterior to ears, distal third of hairs grayish-brown and proximal two-thirds Dark Neutral Gray to base; sides slightly paler than dorsum; ground color of belly Neutral Gray, individual hairs of belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral Gray to Dark Neutral Gray; tips of individual hairs of face Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral vibrissae black to base; forefeet and hind feet sooty above and below, thigh bearing[Pg 646]some white-tipped hairs; tail near Chaetura Drab above, Pale Neutral Gray below; anterior part of jugal projecting slightly ventrally and forming small protuberance at point of articulation with maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal. In most cranial measurements averaging as large asB. t. analogous. Average and extreme measurements of the type and three additional paratypes, all adults, are: total length, 105.5 (101-109); length of tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot, 14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length, 18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length, 6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4); breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of skull, seePlate 2d, andPlate 4e.

Comparisons.—FromB. t. taylori,B. t. fuliginatusdiffers in: dorsum slightly darker than in darkesttaylori; tail densely haired, bicolored rather than unicolored; belly sooty to grayish rather than grayish to whitish; forefeet and hind feet sooty to grayish rather than flesh-colored; incisive foramina less bowed laterally, more nearly straight; interparietal compressed anteroposteriorly, less diamond-shaped.

FromB. t. paulus,B. t. fuliginatusdiffers in: dorsum dusky to blackish rather than fawn color; belly sooty to grayish rather than buffy to whitish-gray; forefeet and hind feet sooty to grayish rather than whitish; zygoma more nearly forming a right angle with rostrum or skull, less tapered anteriorly; anterior part of jugal possessing ventral projection; jugal extending nearly to lacrimal on posterior surface of maxillary part of zygoma.

FromB. t. analogous,B. t. fuliginatusdiffers in: mid-dorsal region blacker, less brownish; tail distinctly bicolored rather than unicolored to faintly bicolored; incisive foramina not constricted medially; presphenoid broader (at narrowest point); jugal differs much the same as it does frompaulus; nasals anteriorly truncate instead of rounded.

Remarks.—Dalquest (1953:155-157) and Booth (1957:15) assigned all of the pygmy mice that they examined from the state of San Luis Potosí toB. t. taylori. Examination of all of the material that was available to Dalquest, plus additional specimens at the University of Kansas Museum of Natural History, reveals that there are three subspecies in San Luis Potosí.B. t. taylorioccurs in the eastern part of the State at lower altitudes;B. t. analogousoccurs to the southeast at higher altitudes;B. t. fuliginatusoccurs in the northeastern part of the State in the Sierra Madre Oriental.

Specimens obtained from Ebano, Pujal, and Tamuín, representative ofB. t. taylori, are much paler on the belly and on the ventral surface of the forefeet and hind feet than are specimens from Ciudad del Maíz, representative ofB. t. fuliginatus. The tail inB. t. tayloriis nearly unicolored and less hairy than in the paratypical series offuliginatus. Specimens from 4 km. NE Ciudad Valles are nearly intermediate in color of the belly, dorsum, forefeet and hindfeet, and tail, between the palest mice from the coastal plain and the darker mice in the mountains of the northeastern part of the State (specimens from El Salto average paler, however, than the type and paratypes). These specimens seem to be intergrades betweenB. t. taylorito the east on the coastal plain andfuliginatusto the northwest in the mountains. It seems best to refer the mice from 4 km. N Ciudad Valles toB. t. taylorion the basis of the average of external and cranial characters. Specimens from 6 mi. SW San Gerónimo, Coahuila, also referred toB. t. taylori, resemble in color the mice from 4 km. N Ciudad Valles. When more specimens are obtained from the front range of the Sierra Madre Oriental, at lower altitudes, the manner in which these two subspecies intergrade with one another will be better understood. At present, populations from higher altitudes in the mountains seem to represent a dark subspecies; populations from the coastal plain represent a pale subspecies, and those from the lower slopes and high valleys seemingly are intergrades.B. t. fuliginatusoccurs in a somewhat limited strip of chernozem soil (or suelos negros of Tamayo, 1949: Carta de Suelos). The populations occurring at lower altitudes on the coastal plain are on generally paler soils.

Specimens examined.—Total 39, all from the Republic of México, as follows:San Luis Potosí: El Salto, 24 Mus. Nat. Hist., Louisiana State Univ., 7 Amer. Mus. Nat. Hist.; type locality, 8 (including the type).Marginal records.—See specimens examined.

Marginal records.—See specimens examined.

Baiomys taylori paulus(J. A. Allen)

Peromyscus paulus, J. A. Allen, Bull. Amer. Mus. Nat. Hist., 19:598, November 12, 1903; Elliot, Field Columb. Mus. Publ., 105(6): 136, July 1, 1905.

Baiomys taylori paulus, Miller, Bull. U. S. Nat. Mus., 79:137, December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924 (part); Ellerman, The Families and Genera of Living Rodents, 2:402, March 21, 1941 (part); Goldman, Smith, Miscl. Coll., 115:373, July 31, 1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist., 26:367, December 15, 1952; Goodwin, Bull. Amer. Mus. Nat. Hist., 102:318, August 31, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955 (part); Packard, Proc. Biol. Soc. Washington, 71:17, April 11, 1958; Packard, Jour. Mamm., 40:146, February 20, 1959; Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 (part).

[Peromyscus]paulus, Elliot, Field Columb, Mus. Publ., 95(4):136, July 15, 1904.

Peromyscus taylori paulus, Osgood, N. Amer. Fauna, 28:255, April 17, 1909 (part).

Peromyscus musculus[musculus], Osgood, N. Amer. Fauna, 28:256, April 17, 1909 (part).

Baiomys taylori[=paulus], Twente and Baker, Jour. Mamm., 32:121, February 15, 1951.

Baiomys musculus musculus, Goldman, Smith. Miscl. Coll., 115:336, July 31, 1951 (part).

Baiomys taylori allex, Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 (part).

Type.—Adult male, skin and skull; No. 21165, American Museum of Natural History; Río Sestín, Durango, Republic of México; obtained on April 15, 1903, by J. H. Batty, original number 455.Range.—Central Chihuahua south through Durango (west to eastern edge of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence west into northern and northwestern Jalisco, seeFigure 11. Zonal range: Lower Sonoran, approximately the Chihuahua Desert Biotic Province of Goldman and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila, Jalisco, up to 6700 feet 2 mi. W Miñaca, Chihuahua.Diagnosis.—Size medium to small for the species; dorsum Buffy Brown to fawn color; dorsal ground color of unworn pelage of adults varying from Buffy Brown in darkest series (especially those from higher altitudes) to Avellaneous with grayish overtones in palest series; worn pelage in mid-dorsal region of adults fawn to grayish; terminal parts of individual hairs buffy, gray basally; guard hairs on dorsum black-tipped, grayish basally; belly Light Gull Gray, distal half of hairs white, proximal half Neutral Gray; hairs in region of throat and chin white to base (some specimens with faint buffy overtones); forefeet dusky below, whitish above; hind feet whitish above, ventral surface whitish to dusky; dorsal and lateral vibrissae black, other vibrissae white. Average and extreme measurements of six adults from the type locality are as follows: total length, 109 (106-117); length of tail, 44.5 (43-48); length of body, 63 (57-69); length of hind foot, 13.1 (12.7-14.0); occipitonasal length, 17.5 (17.4-18.0); zygomatic breadth, 9.3 (9.1-9.5); postpalatal length, 6.6 (6.2-6.9); least interorbital breadth, 3.5 (3.4-3.6); length of incisive foramina, 3.8 (3.6-4.1); length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6 (8.5-8.8); depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of the skull, seePlate 2eandPlate 4f.Comparisons.—For comparisons withB. t. allex,B. t. canutus,B. t. ater, andB. t. taylori, see accounts of those subspecies. FromB. t. analogous,B. t. paulusdiffers as follows: dorsal color paler having more reddish-brown than blackish-brown tones; venter whitish to buffy, instead of gray to light-gray; tail bicolored (not unicolored), usually having more hairs; hind feet white (not sooty) above. Cranially,B. t. paulusdiffers fromB. t. analogousin: skull slightly smaller in all dimensions; maxillary part of zygoma narrowing and forming oblique angle rather than a near right angle with rostrum; anterior incisive foramina constricted posteriorly; tips of nasals truncate (less rounded).

Type.—Adult male, skin and skull; No. 21165, American Museum of Natural History; Río Sestín, Durango, Republic of México; obtained on April 15, 1903, by J. H. Batty, original number 455.

Range.—Central Chihuahua south through Durango (west to eastern edge of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence west into northern and northwestern Jalisco, seeFigure 11. Zonal range: Lower Sonoran, approximately the Chihuahua Desert Biotic Province of Goldman and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila, Jalisco, up to 6700 feet 2 mi. W Miñaca, Chihuahua.

Diagnosis.—Size medium to small for the species; dorsum Buffy Brown to fawn color; dorsal ground color of unworn pelage of adults varying from Buffy Brown in darkest series (especially those from higher altitudes) to Avellaneous with grayish overtones in palest series; worn pelage in mid-dorsal region of adults fawn to grayish; terminal parts of individual hairs buffy, gray basally; guard hairs on dorsum black-tipped, grayish basally; belly Light Gull Gray, distal half of hairs white, proximal half Neutral Gray; hairs in region of throat and chin white to base (some specimens with faint buffy overtones); forefeet dusky below, whitish above; hind feet whitish above, ventral surface whitish to dusky; dorsal and lateral vibrissae black, other vibrissae white. Average and extreme measurements of six adults from the type locality are as follows: total length, 109 (106-117); length of tail, 44.5 (43-48); length of body, 63 (57-69); length of hind foot, 13.1 (12.7-14.0); occipitonasal length, 17.5 (17.4-18.0); zygomatic breadth, 9.3 (9.1-9.5); postpalatal length, 6.6 (6.2-6.9); least interorbital breadth, 3.5 (3.4-3.6); length of incisive foramina, 3.8 (3.6-4.1); length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6 (8.5-8.8); depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of the skull, seePlate 2eandPlate 4f.

Comparisons.—For comparisons withB. t. allex,B. t. canutus,B. t. ater, andB. t. taylori, see accounts of those subspecies. FromB. t. analogous,B. t. paulusdiffers as follows: dorsal color paler having more reddish-brown than blackish-brown tones; venter whitish to buffy, instead of gray to light-gray; tail bicolored (not unicolored), usually having more hairs; hind feet white (not sooty) above. Cranially,B. t. paulusdiffers fromB. t. analogousin: skull slightly smaller in all dimensions; maxillary part of zygoma narrowing and forming oblique angle rather than a near right angle with rostrum; anterior incisive foramina constricted posteriorly; tips of nasals truncate (less rounded).

Remarks.—J. A. Allen (1903:599) correctly pointed out that young specimens, in first pelage, were gray brown; young adults were darker and more varied with some blackish; adults and old adults were buffy to grayish. The change in color of pelage with increasing age is more pronounced inpaulusthan in other subspecies ofB. taylori. Of two males collected on April 12, 1949, one, an adult, is buffy brown, and the other, an old adult with worn pelage, is grayish-brown. In mice in the earlier stages of adulthood,underfur of the dorsum is buffy at the tips and gray basally. With increased wear, the buffy tip is lost. Consequently, mice in the later stages of adulthood are grayish.

B. t. paulusintergrades withaterto the north in Chihuahua (see account of that subspecies), withanalogousto the south in Jalisco, and withallex(see account of that subspecies) to the southwest in Nayarit and Jalisco. The zone of intergradation betweenpaulusandanalogousin Jalisco approximately borders the Río Grande de Santiago from the western part of the State to the northwest shore of Lago de Chapala. Nineteen specimens from 2 mi. WNW Lagos de Moreno in northwest Jalisco seem to be intermediate betweenpaulusandanalogousin color, averaging slightly grayer than typicalpaulus. The series of 19 is referable topauluson the basis of cranial characters.

A series of 34 specimens from 3 mi. W La Venta, Jalisco (referable topaulus), is indistinguishable in color of pelage from two series ofpaulusfrom 5 mi. N Durango, and from 8 mi. NE of Durango, except that the antiplantar surfaces of the hind feet are sooty as inanalogous. Seemingly, features of color mentioned above as diagnostic of the two subspecies are either present or absent and there is no tendency toward intermediacy in color in the population from 3 mi. W La Venta.

The Río Grande de Santiago may have acted in the past as a physical barrier reducing gene flow betweenallexandpaulusand in separating completely the two populations for limited periods.

Specimens examined.—Total 176, all from the Republic of México and distributed as follows:Chihuahua: Rancho Sanignacio, 4 mi. S, 1 mi. W Santo Tomás, 1; El Rosario, 6700 ft., 1; 2 mi. W Miñaca, 6900 ft., 11; Balleza, 1[50].Durango: Rosario, 1[51]; type locality, 14[51](including the type);San Gabriel, 2[51];Rancho Santuario, 2[51]; 1 mi. N Chorro, 6450 ft., 1;8 mi. NE Durango, 6200 ft., 2; 5 mi. N Durango, 6400 ft., 2.Zacatecas: Valparaíso, 6500 ft., 10[50].Aguascalientes:18 mi. W, 2 mi. S Aguascalientes, 6000 ft., 1; 16 mi. S Aguascalientes, 5[52].Jalisco: 1 mi. NE Villa Hidalgo, 6500 ft., 1; 2 mi. WNW Lagos de Moreno, 6370 ft., 19;2 mi. ESE Tequila, 4000 ft., 11;3 mi. W La Venta, 33, 1[53];12 mi. W Guadalajara, 3[54];Atemajac, 12[50]; 4 mi. W Guadalajara, 5100 ft., 3;2 mi. N,1/2mi. W Guadalajara, 11; 2 mi. NW Magdalena, 4500 ft., 7[50];1 mi. N Tala, 4400 ft., 3; 3 mi. W Tala, 4300 ft., 18.Marginal records.—Chihuahua: Rancho Sanignacio, 4 mi. S, 1 mi. W Santo Tomás; El Rosario; Balleza.Durango: Rosario, 6700 ft.; 1 mi. E Zarca (Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft.Zacatecas: Valparaíso, 6500 ft.Aguascalientes: 1 mi. N Chicalote (Blossom and Burt, 1942:4).Jalisco: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W Guadalajara, 5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500 ft.Durango: 5 mi. N Durango, 6400 ft.; type locality.Chihuahua: 2 mi. W Miñaca, 6900 ft.

Marginal records.—Chihuahua: Rancho Sanignacio, 4 mi. S, 1 mi. W Santo Tomás; El Rosario; Balleza.Durango: Rosario, 6700 ft.; 1 mi. E Zarca (Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft.Zacatecas: Valparaíso, 6500 ft.Aguascalientes: 1 mi. N Chicalote (Blossom and Burt, 1942:4).Jalisco: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W Guadalajara, 5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500 ft.Durango: 5 mi. N Durango, 6400 ft.; type locality.Chihuahua: 2 mi. W Miñaca, 6900 ft.

[50]United States National Museum (Biol. Surv. Collections).

[51]American Museum of Natural History.

[52]Univ. Illinois, Mus. Nat. History.

[53]The Museum, Michigan State Univ.

[54]Univ. Michigan, Museum of Zoology.

Baiomys taylori subater(V. Bailey)

Peromyscus taylori subater, V. Bailey, N. Amer. Fauna, 25:102, October 24, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:139, January 15, 1909; Osgood, N. Amer. Fauna, 28:255, April 17, 1909; Elliot, Check-List Mamm. N. Amer. Continent, West Indies and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist, p. 44, January 8, 1917.

Baiomys taylori subater, Miller, Bull. U. S. Nat. Mus., 79:136, December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924; Anthony, Field Book of North American Mammals, p. 348, 1928; Baker, Jour. Mamm., 21:223, May 14, 1940; Ellerman, The Families and Genera of Living Rodents, 2:402, March 21, 1941; Blair, Jour. Mamm., 22:378, November 14, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942; Blair, Jour. Mamm., 23:196, May 14, 1942; Blair and Blossom, Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955; Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959.

Baiomys taylori[=subater], Taylor and Davis, Texas Game, Fish and Oyster Comm. Bull., 27:56, August, 1947 (part).

Type.—Subadult female, skin and skull; No. 32616/44539 U. S. Nat. Mus. (Biol. Surv. Coll.); Bernard Creek, near Columbia, Brazoria County, Texas; obtained on February 25, 1892, by W. Lloyd, original number 1122.Range.—Southeastern Texas, north of Matagorda Bay west to Lavaca County, north to Brazos and Walker counties thence east to Jefferson County, seeFigure 11. Occurs from near sea level in Brazoria and Galveston counties, up to 500 feet in western part of range. Zonal range: Humid division of lower Austral (the western part of the Austroriparian Biotic Province of Dice, 1943:18-21).Diagnosis.—Size medium to large for the species; mid-dorsal region Clove Brown (sooty in freshly captured specimens); some parts of mid-dorsal region all blackish; individual guard hairs of dorsum black-tipped, Deep Neutral Gray basally; underfur black-tipped with subterminal band of light buff, Neutral Gray at base; belly grayish-white, laterally Isabella Color; distal three-fourths of hairs in region of throat and chin white, proximal fourth light gray; in median region of belly distal half of individual hairs white, proximal half dark gray; vibrissae in most specimens black to base. Average and extreme cranial measurements of six adults from 7 mi. S La Belle are as follows: occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6 (9.1-9.9); postpalatal length, 6.8 (6.2-7.2); least interorbital breadth, 3.7 (3.4-3.9); length of incisive foramina, 4.0 (3.6-4.2); length of rostrum, 6.5 (6.1-6.8); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.7 (6.6-6.8); alveolar length of maxillary tooth-row, 3.1 (2.9-3.2). Average and extreme external measurements of four adults from Richmond are as follows: total length, 111.5 (108-118); length of tail vertebrae, 43.5 (41-47); length of body, 68 (67-71); length of hind foot, 14 (13-15); for photographs of the skull, seePlate 2f, andPlate 4g.Comparisons.—BecauseB. t. subaterintergrades only withB. t. taylorito the south and west,subateris compared only withtaylori. Young adults of both subspecies in unworn pelage show best the colors that differentiate the two subspecies. Old adults ofsubaterin worn pelage appear grayish, resemblingtaylori, and at that age, only certain cranial characters are of taxonomic use. Cranially,subaterdiffers fromtayloriin: presphenoid not shaped like an hour-glass; parapterygoid processes thicker medially; interparietal diamond-shaped instead of elongated and compressed. Skull slightly larger in most measurements.

Range.—Southeastern Texas, north of Matagorda Bay west to Lavaca County, north to Brazos and Walker counties thence east to Jefferson County, seeFigure 11. Occurs from near sea level in Brazoria and Galveston counties, up to 500 feet in western part of range. Zonal range: Humid division of lower Austral (the western part of the Austroriparian Biotic Province of Dice, 1943:18-21).

Diagnosis.—Size medium to large for the species; mid-dorsal region Clove Brown (sooty in freshly captured specimens); some parts of mid-dorsal region all blackish; individual guard hairs of dorsum black-tipped, Deep Neutral Gray basally; underfur black-tipped with subterminal band of light buff, Neutral Gray at base; belly grayish-white, laterally Isabella Color; distal three-fourths of hairs in region of throat and chin white, proximal fourth light gray; in median region of belly distal half of individual hairs white, proximal half dark gray; vibrissae in most specimens black to base. Average and extreme cranial measurements of six adults from 7 mi. S La Belle are as follows: occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6 (9.1-9.9); postpalatal length, 6.8 (6.2-7.2); least interorbital breadth, 3.7 (3.4-3.9); length of incisive foramina, 4.0 (3.6-4.2); length of rostrum, 6.5 (6.1-6.8); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.7 (6.6-6.8); alveolar length of maxillary tooth-row, 3.1 (2.9-3.2). Average and extreme external measurements of four adults from Richmond are as follows: total length, 111.5 (108-118); length of tail vertebrae, 43.5 (41-47); length of body, 68 (67-71); length of hind foot, 14 (13-15); for photographs of the skull, seePlate 2f, andPlate 4g.

Comparisons.—BecauseB. t. subaterintergrades only withB. t. taylorito the south and west,subateris compared only withtaylori. Young adults of both subspecies in unworn pelage show best the colors that differentiate the two subspecies. Old adults ofsubaterin worn pelage appear grayish, resemblingtaylori, and at that age, only certain cranial characters are of taxonomic use. Cranially,subaterdiffers fromtayloriin: presphenoid not shaped like an hour-glass; parapterygoid processes thicker medially; interparietal diamond-shaped instead of elongated and compressed. Skull slightly larger in most measurements.

PLATE 1

PLATE 2

PLATE 3

PLATE 4

Remarks.—This subspecies retains its chief diagnostic character, blackish mid-dorsal region, throughout nearly all parts of its range. Specimens from the general area of Matagorda Bay and Lavaca County grade intotayloriin characters of color and crania. The Colorado and Brazos rivers seemingly serve as barriers reducing gene flow betweentayloriandsubater. These rivers may well have been important factors in the origin and the limitation of these two seemingly closely-related subspecies.

Baiomys taylori subateris not differentiated in color of pelage and characters of crania fromB. t. taylorito the same degree thatB. t. paulusis differentiated fromB. t. analogous, or thatB. t. tayloriis differentiated from several of the other subspecies ofBaiomys taylori.B. t. subaterprobably is a more recent occupant of the area in which it now lives than is the case with any other one of the subspecies oftaylori. Sufficient time probably has not elapsed to allow for formation of more distinctive phenotypic patterns.

Specimens examined.—Total 65, all fromTexasand distributed as follows:Brazos County:1/2mi. NW College Station, 1[55];3 mi. W College Station,1 mi. W Easterwood Airport, 1[55];College Station, 1[55].Walker County: Huntsville, 1[55].Hardin County: Sour Lake, 1[57].Jefferson County: 7 mi. S Labelle, 10.Harris County: 6 mi. NE Crosby, 1[56].Colorado County:10 mi. N Eagle Lake, 1[55];9 mi. N Eagle Lake, 1[55]; 2 mi. W Eagle Lake, 1;Eagle Lake, 1[55], 5.Fort Bend County: Richmond, 4[57].Galveston County:Texas City, 6[58]; Virginia Point, 1[57].Brazoria County:Austin Bayou near Alvin, 2[57]; 14 mi. SSE Alvin, 2[59]; type locality, 7[57](including the type).Lavaca County: 4 mi. W Hallettsville, 1[55];1 mi. SW Hallettsville, 3[55];13.7 mi. SW Hallettsville, 2[55]; 4 mi. NE Yoakum, 11.Marginal records.—Texas: Huntsville; Sour Lake; 7 mi. S La Belle; Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi. W Hallettsville;1/2mi. NW College Station.

Marginal records.—Texas: Huntsville; Sour Lake; 7 mi. S La Belle; Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi. W Hallettsville;1/2mi. NW College Station.

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