Chapter 3

Fig. 1. Calling male of Rhinophrynus dorsalis, photographed in a pond north of Santa Cruz, Oaxaca, on July 6, 1958. × 2/3.Fig. 1.Calling male ofRhinophrynus dorsalis, photographed in a pond north of Santa Cruz, Oaxaca, on July 6, 1958. × 2/3.

Fig. 2. Color pattern variation in two adults of Bufo canaliferus from Juchitán, Oaxaca. × 2/3.Fig. 2.Color pattern variation in two adults ofBufo canaliferusfrom Juchitán, Oaxaca. × 2/3.

PLATE 7

Fig. 1. Calling male of Engystomops pustulosus, photographed in a pond west of Tehuantepec, Oaxaca, on July 5, 1956. × 2.Fig. 1.Calling male ofEngystomops pustulosus, photographed in a pond west of Tehuantepec, Oaxaca, on July 5, 1956. × 2.

Fig. 2. Foamy egg mass of Engystomops pustulosus at the edge of a pond west of Tehuantepec, Oaxaca. July 5, 1956. × 3/8.Fig. 2.Foamy egg mass ofEngystomops pustulosusat the edge of a pond west of Tehuantepec, Oaxaca. July 5, 1956. × 3/8.

PLATE 8

Fig. 1. Calling male of Diaglena reticulata, photographed at a pond north of Salina Cruz, Oaxaca, on July 6, 1958. × 1/2.Fig. 1.Calling male ofDiaglena reticulata, photographed at a pond north of Salina Cruz, Oaxaca, on July 6, 1958. × 1/2.

Fig. 2. Clasping pair of Diaglena reticulata at the edge of a pond north of Salina Cruz, Oaxaca, on July 6, 1958. × 1.Fig. 2.Clasping pair ofDiaglena reticulataat the edge of a pond north of Salina Cruz, Oaxaca, on July 6, 1958. × 1.

Breeding congregations were found after heavy rains at Tehuantepec on July 5, 1956, at Cosamaloapan, Novillero, and Amatitlán on July 26, 1956, and at Salina Cruz on July 6, 1958. The call is a long "worrp" made while the male is floating on the surface of the pond. The small heads, small limbs, and greatly inflated bodies cause the calling males to resemble miniature caricature balloons (Pl. 6, fig. 1). Amplexus is inguinal. These toads are notably wary, even when calling. Often the beam of a flashlight or the slightest disturbance of the water will cause the males to stop calling. The body is deflated with one last nauseous note, and the frog sinks beneath the surface of the water and swims away with short slow kicks of the hind feet.

Bufo canaliferusCope

Oaxaca: Chivela; Salina Cruz; Santa Efigenia; Tapanatepec (6); Tehuantepec (10); Zanatepec (4).

This small toad apparently is restricted to the Pacific lowlands from the Isthmus of Tehuantepec eastward to Guatemala. At Zanatepec on July 13, 1956, males were calling from a flooded field bordered by scrub forest. The call is a rather loud nasal racket. Living individuals vary greatly in coloration. Some have yellowish tan flanks and dorsum and an orange middorsal stripe; others have a pale red dorsum, yellow flanks, and a cream middorsal stripe (Pl. 6, fig. 2).

Bufo cocciferCope

Oaxaca: Juchitán (5); Tehuantepec.

It is with some degree of hesitancy that these toads are referred to the speciescoccifer. Although these and other specimens from Guerrero and Michoacán display no striking differences from specimens from Costa Rica, Nicaragua, and southeastern Guatemala, the ranges of the populations are separated by a broad hiatus in Chiapas and Guatemala. Possibly this species has utilized the sub-humid corridor through northern Central America (Stuart, 1954) and subsequently disappeared from the corridor in Guatemala and Chiapas. Specimens of acoccifer-like toad collected by Stuart in the vicinity of Jacaltenango, Departamento Huehuetenango, Guatemala, are much larger than either the Central American or Mexican specimens ofcoccifer. A final commitment on the systematic status must await a thorough study of this group of toads.

Males of this species were calling from a grassy rain-pool in open scrub forest at the edge of Juchitán on July 6, 1956. The call is a low"whirrr." The calling males were sitting in the shallow water at the edge of pond, where they were hidden by the grass. None was observed in open water, as is characteristic of calling males ofBufo canaliferusandmarmoreus.

Bufo marinusLinnaeus

Oaxaca: Agua Caliente; Guichicovi (3); Mixtequilla; Tolosita (6); Tehuantepec (37); Tuxtepec; Unión Hidalgo.Veracruz: Ciudad Alemán (4); Cosamaloapan; Cuatotolapam (19); 20 km. SE of Jesús Carranza (4); 38 km. SE of Jesús Carranza (10); 20 km. NE of Jesús Carranza (4); Novillero.

This large toad is abundant throughout the lowlands of the isthmus. The loud rattling call of males was heard on rainy nights throughout the summer. In March, 1956, several adults were found in a small cave back of a spring at Agua Caliente.

Bufo marmoreusWiegmann

Oaxaca: Cerro San Pedro (2); Chivela (5); Escurano (3); Juchitán; Salina Cruz (101); Santa Lucía (2); 12 km. S of Santiago Chivela (11); Santo Domingo; Tapanatepec; Tehuantepec (100); Tequisistlán.Veracruz: Alvarado; Coatzacoalcos.

This toad is abundant on the Pacific lowlands, where it inhabits both open and dense scrub forest. On the Gulf lowlands its distribution seems to be limited to xeric coastal habitats. Aside from the specimens from Alvarado and Coatzacoalcos, it is known in Veracruz only from Boca del Río (Langebartel and Smith, 1959:27).

The similarity in size ofBufo marmoreusandvallicepsand their almost completely allopatric ranges suggest that the two species may be in competition at any one locality. Nevertheless, both were calling from a small rocky stream south of Santiago Chivela on July 6, 1956.

On the night of July 6, 1958, an estimated 400 toads of this species made up a breeding congregation near Salina Cruz. The site was a shallow muddy pond about 20 × 40 meters located in an area cleared of scrub forest; the banks of the pond were devoid of vegetation (Pl. 5, fig. 2). Breeding in the same pond wereRhinophrynus dorsalisandDiaglena reticulata. The following morning no more than a dozenBufowere found in the pond, but several individuals were found beneath debris and in small burrows near the pond. On July 7, 1958, large numbers of tadpoles and recently metamorphosed young were in a shallow grassy pool just east of Salina Cruz.

Taylor (1943b:347) referred certain specimens from Tehuantepec toBufo perplexus, a species closely related toBufo marmoreus.Evidence to be presented elsewhere shows thatperplexusdoes not occur in the isthmus.

Bufo valliceps vallicepsWiegmann

Oaxaca: Guichicovi (2); Matías Romero; 32 km. N of Matías Romero (2); Nueva Raza; Río Sarabia (3); Santa María Chimalapa (14); Santiago Chivela; 12 km. S of Santiago Chivela (5); Santo Domingo (5); Tolosita (7).Veracruz: Acayucan (3); Alvarado; Amatitlán; Ayentes; Cosamaloapan (3); Cosoleacaque (6); Cuatotolapam (14); Hueyapan; 20 km. ENE of Jesús Carranza (6); 20 km. S of Jesús Carranza; 25 km. SE of Jesús Carranza (23); 35 km. SE of Jesús Carranza; 60 km. SW of Jesús Carranza (5); La Oaxaqueña (4); Novillero (4); San Lorenzo (5).

Individuals were found in both wet and dry seasons. In the dry season they were most frequently found in rainforest, whereas in the rainy season breeding congregations were found in savannas as well. This toad occurs throughout the Gulf lowlands and on the Pacific slopes and in the Grijalva Valley of Chiapas and Guatemala, but not on the Pacific lowlands of the isthmus.

I have not been able to recognize individuals referrable to the racemacrocristatus. Firschein and Smith (1957:219) describedmacrocristatusfrom the mountains of eastern Oaxaca and referred to it specimens from the Gulf lowlands of northern Chiapas. None of the present material shows the hypertrophied cranial crests supposedly characteristic ofmacroaristatus, nor do specimens from the isthmus resemble the population in the Grijalva Valley being described by L. C. Stuart, who will discuss the variation in, and the validity of, the named populations ofvalliceps.

Five specimens from San Lorenzo, Veracruz (USNM 123516-20), were identified asBufo cristatusby Smith (1947:408). Firschein (1950:83) redefined thecristatusgroup ofBufoand assigned these specimens tovalliceps.

Eleutherodactylus alfrediBoulenger

Oaxaca: Tolosita (2).Veracruz: 35 km. SE of Jesús Carranza (6).

These specimens were collected in rainforest. Shreve (1957:247) pointed out the close resemblance betweenE. alfrediandE. conspicuusfrom Piedras Negras, Guatemala, and treated them as subspecies. Examination of the specimens from the isthmus, together with seven from central Veracruz and one from Teapa, Tabasco, suggests an even closer relationship.Eleutherodactylus conspicuuswas diagnosed by Taylor and Smith (1945:567) as differing fromalfredi"in lacking a tarsal fold, in having shorter hind legs with the tibiotarsal articulation reaching only to the nostril instead of beyond the tip of the snout; the vomerine teeth barely reach the posterior level of the choanae." The specimen fromTeapa has the vomerine teeth reaching to the posterior edge of the choanae; in the eight specimens from the isthmus the teeth reach the posterior edge of the choanae in two and to the middle of the choanae in six; in seven specimens from central Veracruz the teeth reach the posterior edge of the choanae in two and to the middle in five. The tibiotarsal articulation extends beyond the tip of the snout in the specimen from Teapa and in two from central Veracruz; in three specimens from the isthmus and in one from central Veracruz it extends only to the nostril; in the others it extends to the snout. The tarsal fold is absent in the specimen from Teapa, in three from the isthmus, and in all those from central Veracruz; it is weakly present in the others.

In the light of this evidence there seems to be little justification in recognizing two species or even two subspecies in this group. Consequently,Eleutherodactylus conspicuusTaylor and Smith (1945) is here placed in the synonymy ofEleutherodactylus alfrediBoulenger (1898), a species with a range extending from Cuautlapan and Potrero Viejo in central Veracruz southward and eastward in forested habitats to western El Petén, Guatemala.

Eleutherodactylus natatorTaylor

Veracruz: 35 km. SE of Jesús Carranza (3); 38 km. S of Jesús Carranza; 55 km. SE of Jesús Carranza.

The snout-vent length is 42.0 mm. in a male and averages 59.5 mm. in three adult females. The tarsal fold is low and extends about half the length of the tarsus; the first and second fingers are subequal in length; the tibiotarsal articulation extends beyond the tip of the snout. The patches of vomerine teeth lie between the posterior margins of the choanae. The throat and belly are immaculate, and the soles of the feet are dark. In the isthmus this species can be distinguished fromEleutherodactylus rugulosusby less rugose skin on the dorsum and absence of dark ventral mottling.

The specimens reported here extend the known range ofnatatoreastward from Camotlán, Oaxaca; northward in Veracruz the species inhabits foothills as far north as Huatusco.

Eleutherodactylus rhodopisCope

Oaxaca: 30 km. N of Matías Romero; Río Sarabia (5); Tapanatepec (87); Tolosita (6); between Zanatepec and Tapanatepec.Veracruz: 25 km. SE of Jesús Carranza; 35 km. SE of Jesús Carranza (2); 22 km. SSW of Jesús Carranza; 20 km. ENE of Jesús Carranza (7); Minatitlán; Tapalapan (5).

For the purposes of the present study I am not recognizingEleutherodactylus beati,E. dorsoconcolor, andE. venustusas specifically,or even subspecifically distinct from the earlier namedE. rhodopis. Probably these are mere color varieties of a single species.

In the dry season frogs of this species were in humid forests, where they were most frequently found along small streams and in ravines. The species is widespread in the Gulf lowlands, but does not occur on the Plains of Tehuantepec. It does inhabit the Pacific slopes on the foothills of the Sierra Madre de Chiapas, the western part of which extends into eastern Oaxaca near Tapanatepec.

Eleutherodactylus rugulosusCope

Oaxaca: La Princesa (30); Modelo; Santa Lucía (10); Tapanatepec (26); Tehuantepec (6); Tres Cruces (8).Veracruz: Tapalapan (5).

In addition to the specimens from the lowlands of the isthmus, for the purposes of the following discussion, I have included data on two specimens from the southern slopes of the Sierra del Sur in Oaxaca (Mirador and Chacalapa) and on several specimens from Los Tuxtlas in Veracruz (Los Chaneques, 67; Salto de Eyipantla, 35; and San Andrés Tuxtla, 11).

Frogs of theEleutherodactylus rugulosuscomplex occur from southern Veracruz and Sinaloa southward through Central America. Taylor (1940:401) describedE. vocalisfrom Hacienda El Sabino, Michoacán; Taylor and Smith (1945:580) describedE. avocalisfrom Tres Cruces, Oaxaca. These have been considered as species distinct fromrugulosus, which is known to occur in Veracruz, Guerrero, and Chiapas southward into Central America. Although the large number of specimens collected in the isthmus does not aid in defining the ranges of the taxa involved, these specimens do give some idea of the variation in certain characters in a given population.

In specimens from Los Tuxtlas the tarsal fold is well-developed and extends two-thirds to three-fourths the length of the tarsus; the tibiotarsal articulation reaches the nostril and sometimes slightly beyond the tip of the snout. In males the tympanum is nearly equal to the diameter of the eye; in females it is about one-half the diameter of the eye. The posterior surfaces of the thighs are dark brown or black with whitish or cream-colored spots, flecks, or irregular mottling. The tarsal fold is dark; the throat is pale in some individuals, but in most is mottled with dark brown or gray flecks. Individuals from La Princesa near the continental divide in Oaxaca show the same variation in body proportions and development of the tarsal fold. The posterior surfaces of the thighs are dark brownindistinctly mottled with lighter brown. The throat is dark brown. Specimens from the Pacific slopes of Oaxaca, including the Plains of Tehuantepec, have dark brown thighs mottled with dusty cream. The tibiotarsal articulation extends slightly beyond the tip of the snout in all specimens. In males the tympanum is equal to about two-thirds the diameter of the eye. Duellman (1958b:6) discussed the variation in these characters in populations in Colima, Jalisco, and Michoacán.

Until the extent of variation of these characters is known throughout the range ofrugulosus, the recognition of populations either as species or subspecies seems superfluous. Consequently, I have used the oldest name; this does not necessarily imply, however, that all populations ofrugulosus(sensu lato) are conspecific.

Of the 200 specimens examined, 15 have a middorsal stripe that is red or yellow. The iris varies from a copper to a dark golden color and shines bright red at night. Many of the specimens are juveniles; these were collected in the dry season, at which time they were found beneath rocks along streams, in road culverts where there was some water, and in holes in banks and cliffs.

Microbatrachylus pygmaeusTaylor

Oaxaca: La Princesa (5); Matías Romero (9); Río Sarabia (41); Tolosita (2).Veracruz: Jesús Carranza; 20 km. ENE of Jesús Carranza.

The specimens listed above vary widely in color patterns; some of the patterns are characteristic of certain named "species":albolabris,imitator,lineatissimus, andminimus. The large series from the Río Sarabia contains all of the color patterns; this series was obtained in one small ravine in the rainforest. At least in the isthmian region, this species does not inhabit the Pacific slopes and lowlands.

Syrrhophus leprusCope

Oaxaca: 33 km. N of Matías Romero; Santa Efigenia.Veracruz: San Lorenzo.

Although the type locality is stated to be Santa Efigenia on the Pacific slopes of the Sierra Madre de Chiapas in eastern Oaxaca, the type specimen probably came from the northern slopes of the mountains. All other known specimens are from the Gulf slopes and lowlands, and from several localities in Los Tuxtlas. Details concerning specimens from the isthmus and other parts of the range were given by Duellman (1958c:8).

Smith (1947:408) reported a specimen ofSyrrhophus verruculatusPeters from San Lorenzo, Veracruz; he stated that this specimen(USNM 123530) could not beS. leprus, because it had a gray belly, norS. cystignathoides, because of the dark and light dorsal coloration. Firschein (1954:57) in his review of the species ofSyrrhophusin eastern México referred the specimen toS. cystignathoides. The specimen is in poor condition. Nevertheless, specific determination is possible. Numerous specimens ofS. leprusfrom Los Tuxtlas have gray bellies; some have heavier pigmentation than the specimen from San Lorenzo. In preservative the dorsum is dark brown with lighter mottling. There is little doubt that the specimen from San Lorenzo is aSyrrhophus leprus, an abundant and widespread species in the humid Gulf lowlands of southern México, and notverruculatus, if this is a valid species (see Firschein,op. cit.:58), and notcystignathoides, a species known from San Luis Potosí southward to central Veracruz.

Syrrhophus pipilans pipilansTaylor

Oaxaca: Cerro Arenal; Cerro San Pedro; 6 km. N of Chivela; 14 km. W of Tehuantepec (2).

In the isthmian region this frog is known only from the Pacific slopes and the Plains of Tehuantepec. Males call from the ground and from trees to heights of about four meters. The call is a single, high, long "peep."

Engystomops pustulosusCope

Oaxaca: Chivela; La Ventosa (3); Santo Domingo; Tapanatepec (14); Tehuantepec (61); Unión Hidalgo (62).Veracruz: Acayucan; Cuatotolapam (7); 10 km. SE of Hueyapan (11).

Large congregations were breeding at Tehuantepec on July 5, at Tapanatepec on July 13, and at Hueyapan on July 24, 1956. The frogs were breeding in open ponds in scrub forest and savanna; none was found in the rainforest. Males call while floating on the water (Pl. 7, fig. 1); the call is a soft "do-ing, do-ing" with a rising tone on the last note. Numerous individual egg masses were along the bank of a pond near Tehuantepec; one large composite egg mass there had a surface area of about one square meter (Pl. 7, fig. 2). The large series from Unión Hidalgo was obtained by digging specimens out of a dry sandy river bank in the dry season. Some of the individuals were buried to a depth of 25 centimeters.

In life individuals from the Pacific lowlands were dull brown and gray; those from Acayucan were dark chocolate brown to black with pink or red blotches, forearms, and dorsal stripe. Not all specimens from the Atlantic lowlands are so colored; individualsfrom Cordoba and Mirador, Veracruz, are like those from Tehuantepec.

Leptodactylus labialisCope

Oaxaca: Agua Caliente; Chivela (2); Matías Romero (12); 33 km. N of Matías Romero (4); Mixtequilla; Santa Efigenia; Tapanatepec; Tehuantepec (38); Tolosita (2); 33 km. W of Zanatepec (49).Veracruz: Acayucan (3); Ciudad Alemán; Cuatotolapam (10); Hueyapan; La Oaxaqueña (4); 38 km. SE of Jesús Carranza; 20 km. ENE of Jesús Carranza; Novillero (3); San Lorenzo (2).

AlthoughLeptodactylus labialisdoes not appear to be so abundant asLeptodactylus melanonotus, the former was found throughout the lowlands of the isthmus. In the dry season individuals were found along streams, and in the rainy season breeding congregations were found in rain pools, marshes, ponds, and even small puddles. The call is a slow "wort, wort, wort." Males call beneath the water and from beneath rocks and from holes in the ground. The average snout-vent length of eight adult males is 37.2 mm. A completely metamorphosed juvenile obtained at Hueyapan on July 24, 1956, has a snout-vent length of 11 mm.

Leptodactylus melanonotusHallowell

Oaxaca: Agua Caliente (25); Cerro Arenal (2); Cerro Quiengola (3); Cerro San Pedro (3); Chivela (2); Coyol; Juchitán; Matías Romero (11); Mixtequilla (2); Papaloapan (2); Salazar (9); Salina Cruz; 11 km. S of Santiago Chivela; Tapanatepec (17); Tehuantepec (176); Tolosita; Unión Hidalgo; 27 km. W of Zanatepec (6).Veracruz: Acayucan; Cuatotolapam (9); Cosoleacaque; 20 km. ENE of Jesús Carranza (2); 20 km. SE of Minatitlán (2); Novillero; San Lorenzo (6).

This frog is abundant throughout the lowlands of the isthmus, where in the dry season individuals were found along streams and beneath rocks at a spring seepage. In the rainy season males were calling from nearly every bit of standing water. The call is a soft clicking sound resembling that made by striking two small stones together. The average snout-vent length of ten adult males is 41.8 mm. There is considerable variation in the extent of the yellowish brown glandular areas on the belly. Some have none, whereas others have a broad area on the chest, a band along the flanks, and a thin band across the lower abdomen. Individuals collected in the dry season vary in the same fashion as do those collected in the rainy season, at which time they were breeding. The glands are equally well-developed in adults of both sexes, and were present in some juveniles with snout-vent lengths of less than 20 mm. Apparently the development of the glands is not associated with maturity, sex, or size.

Diaglena reticulataTaylor

Oaxaca: Cerro Arenal; Chivela; Salina Cruz (26); San Antonio (3); Tehuantepec (2); 8.6 km. W of Tehuantepec (11); Zarzamora.

Breeding congregations of this rare frog were found 8.6 kilometers west of Tehuantepec on July 5, 1956, and at Salina Cruz on July 6, 1958. Both choruses took place immediately after torrential rains. In both instances the frogs were in and about open muddy pools in the scrub forest (Pl. 5, fig. 2); males called from the bank near the water, and clasping pairs were found only on land (Pl. 8, figs. 1-2). The call is a loud, nasal "braaa," two to three seconds in duration. Amplexus is axillary.

The dorsal ground color is light yellowish green tending towards olive on the head and fading to yellow on the flanks. The ventral surfaces, including the vocal sac, are white; the iris is golden and flecked with black. The present series agrees well with the description ofreticulata(based on two specimens) given by Taylor (1942:60). A detailed analysis of variation, comparison with related species, and descriptions of tadpoles are reserved for a future report.

Hyla baudiniDuméril and Bibron

Oaxaca: Bisilana; Cerro Quiengola (2); Cerro San Pedro; Coyol; Matías Romero (12); Mixtequilla; Río Sarabia (7); Salazar; San Antonio; 11 km. S of Santiago Chivela; Santo Domingo (3); Tapanatepec (2); Tehuantepec (23); Tolosita.Veracruz: Acayucan; Amatitlán; Ciudad Alemán (3); Cosamaloapan (2); Cuatotolapam (15); 10 km. SE of Hueyapan; 20 km. S of Jesús Carranza; 38 km. S of Jesús Carranza (2); 20 km. ENE of Jesús Carranza (4); La Oaxaqueña (2); Minatitlán (2); Naranja (3); Novillero (9); Río de las Playas (2); San Lorenzo (5); Tapalapan (2).

Commonly found on both sides of the isthmus, this large tree frog nearly always is associated with trees; it is not found in the savannas, although it breeds in savannas adjacent to rainforest. It appears to be somewhat more abundant in scrub forest than in rainforest. In the daytime individuals were found under the outer sheaths of banana plants, in the axils of leaves of elephant ears (Xanthosoma), in cavities in trees, and on shaded limbs in the forest. Recently metamorphosed individuals having snout-vent lengths slightly more than 20 mm. were found in the latter part of July.

Hyla ebraccataCope

Oaxaca: Donají (17); 43 km. N of Matías Romero (27); Sarabia (6); Tolosita (3); Ubero (17).Veracruz: Aquilera.

This small species was found only in forested areas, where calling males were on bushes and trees around rain pools. The callis a harsh squawk repeated at intervals of 15 to 20 seconds, followed by a minute or more of silence, and then repeated. Clasping pairs were found on bushes and in the water.

The dorsum bears a dark chocolate brown hour glass-shaped mark, which in some individuals is broken into a large mark posteriorly and a smaller triangular one on the head and nape. The dorsal ground color varies from pale cream or ivory to yellow or tan. The intensity of the dorsal pigmentation is subject to rather rapid change. The flanks, hands, and anterior part of the venter are lemon yellow; the feet, thighs, and posterior part of the venter are golden yellow. The dorsal surface of the shank is yellow to tan with chocolate brown bars or spots; the heel is pale yellow. There is a dark brown bar in the loreal region and a dark brown bar extending posteriorly from the eye to a point above the insertion of the forelimb. The iris is a copper color. The toes are completely webbed; the fingers, one-third webbed. There is a small axillary web that is evident when the forelimbs are at right angles to the body. Twenty males have an average snout-vent length of 28.1 mm.; three females, 35.3 mm. There are no nuptial tuberosities on the pollex of breeding males.

This species has been collected at Coyame and Catemaco in Los Tuxtlas and at various localities in Tabasco; it apparently ranges eastward from southern Veracruz, México, in humid forests to El Petén, Guatemala.

Hyla loquaxGaige and Stuart

Oaxaca: Donají (7); 43 km. N of Matías Romero (21).Veracruz: 19 km. N of Acayucan (4); Aquilera (3); 8 km. SW of Coatzacoalcos (36); Cuototolapam (11); Naranja (13); San Lorenzo (8).

In the isthmus this species is known only from the humid forests of the Gulf lowlands; it is also known from Boca del Río, Veracruz, and from Teapa and Villa Hermosa, Tabasco.

Calling males were found on aquatic plants above the water in deep ponds in the forest where it was necessary for the collector to wade waist-deep in water to obtain them. The call is a loud "hah-onk." Individuals, when active at night, are yellowish tan above with light olive green spots. The flanks, belly, and vocal sac are yellow, and the anterior and posterior surfaces of the thighs and webbing of the feet are bright orange-red or tomato red. Individuals found during the day are grayish brown with olive markings or reddish brown with black markings. Sleeping individuals are ivory-gray with faint gray markings. The iris is a bright copper color. Fifteen adult males have an average snout-vent length of41.7 mm.; they have no horny nuptial pads on the pollex.

The relationships of this species are withHyla rickardsiTaylor, a species known only from the foothills of the Sierra Madre Oriental in the states of Puebla and Veracruz. The distinguishing characteristics of these species are given in Table 1. Living individuals may be distinguished immediately by the flash colors on the thighs—red inloquaxand yellow inrickardsi. The calls of the two species are distinctly different; that ofrickardsiis a high-pitched, loud rattle continued for several seconds, notably different from the goose-like honk ofloquax.

Table 1.—Comparison of Certain Characters in Hyla loquax and Hyla rickardsi

CharacterloquaxrickardsiToe webbingFullThree-fourthsFinger webbingThree-fourthsOne-halfAverage snout-vent length (♂)41.7 mm.37.4 mm.Tympanum/eye (♂)63.2%55.8%Dorsal leg patternBarredUnmarkedTarsal foldTubercularAbsentTarsal stripeAbsent or indistinctBroad, indistinct, or absentDorsolateral stripeAbsentPresentLight line over anusBroadNarrowFlash colorsRedYellowIris colorCopperBronze

The three specimens from San Lorenzo, Veracruz (USNM 123513-5), were identified asHyla rickardsiby Smith (1947:409). The flash colors have faded in preservative, and so are of no aid in identifying these specimens. Two are adult females with snout-vent lengths of 35 and 39 mm. In possessing a relatively large tympanum and barred thighs, and in lacking a dorsolateral stripe they are typical ofloquax, but in the amount of webbing on the hands and feet, broad tarsal stripe, and narrow anal stripe they are likerickardsi. The third specimen, a juvenile, has a snout-vent length of 25 mm. In coloration it resembles the adults; it has more distinctbars on the limbs. On the basis of geography these specimens should beloquax, for the closest known record ofrickardsiis more than 200 kilometers to the northwest, whereasloquaxis known from several localities around San Lorenzo.

Shannon and Werler (1955:383) describedHyla axillamembranafrom the lower southern slopes of Los Tuxtlas. The unique type is a small male (27 mm. snout-vent). I have examined the type and find no great differences between it and small specimens ofloquax. It is not possible to determine the color of the thighs, nor was this information given in the description.Hyla axillamembranais here considered to be a synonym ofHyla loquax.

Hyla microcephala martiniSmith

Oaxaca: Donají (15); 43 km. N of Matías Romero (19); Río Sarabia (2); Sarabia (11); Tolosita.Veracruz: Acayucan (17); Alvarado (41); Aquilera (21); 8 km. SW of Coatzacoalcos (10); Cosoleacaque (26); 10 km. SE of Hueyapan; Naranja (3); Novillero.

This frog is abundant in the Gulf lowlands of the isthmus, where large breeding congregations were found in grassy ponds on the savannas and in openings in the forest. Most frequently males were calling from grasses and reeds in the ponds; many individuals were perched precariously on thin blades as high as one meter above the water. The call is a series of low squeaks.

Individuals found at night were pale yellow above with light brown lines arranged in an irregular pattern on the back, but often forming a cross or an X-shaped mark in the scapular region. There is a brown stripe from the nostril to the eye and thence to the groin. Anteriorly this stripe is bordered above by a thin white or cream-colored line. Numerous small brown flecks are scattered on the back and dorsal surface of the shank. In most specimens there are thin transverse brown bars on the shank. The thighs and undersides of the limbs are golden yellow; the belly and vocal sac are lemon yellow. The iris is yellowish brown. During the day individuals assume a pale reddish tan ground color with darker brown markings. Twenty-five adult males from Alvarado have an average snout-vent length of 24.1 mm.

Hyla pictaGünther

Oaxaca: Donají (8); Sarabia (11); Tolosita (15); Ubero (6).Veracruz: 19 km. N of Acayucan (4); Alvarado (5); Aquilera; 8 km. SW of Coatzacoalcos; 10 km. SE of Hueyapan (7); Lerdo de Tejada; Tula (3).

Widespread in the forests, scrub, and savannas on the Gulf lowlands of the isthmus, these frogs were found breeding at numerous localities. Males call from grasses and bushes growing in andabout ponds. The call is a high-pitched insect-like trill. At night these frogs are pale yellow above; they change to light grayish tan during the day. A dark stripe extends from the nostril to the eye and thence posteriorly to a point between the axilla and groin. Above this dark stripe is a broader white stripe. Scattered on the dorsum are brown flecks or spots; the shanks are marked with poorly-defined cross-bars. The thighs are deep yellow below and paler above with scattered dark flecks. The belly is white, and the vocal sac is yellow. The iris is golden. Twenty males have an average snout-vent length of 21.5 mm.; three females, 24.0 mm.

Hyla robertmertensiTaylor

Oaxaca: Tapanatepec (28); 7.5 km. NW of Tapanatepec (38); 7.2 km. WNW of Zanatepec (77).

This species was found in the isthmian region only on the Pacific lowlands at the southern base of the western part of the Sierra Madre de Chiapas. On July 13, 1956, many large choruses were discovered. The calling males were on reeds and thorn scrub in and at the edge of temporary ponds; the call is a cricket-like "creak-creack," quickly followed by a series of notes "creak-eek-eek-eek-eek."

At night the dorsal ground color is pale yellow; this changes to pinkish buff during the day. There is a grayish or brown dark stripe from the nostril to the eye; the stripe continues to the groin. This dark stripe is bordered above by a narrow white stripe. The belly is white, and the vocal sac is yellow. The iris is dull reddish brown. Twenty-five males have an average snout-vent length of 24.7 mm.

Hyla staufferiCope

Oaxaca: Chivela; Huilotepec (5); Juchitán (4); Matías Romero (4); 25 km. N of Matías Romero; Mixtequilla (4); Río Sarabia (11); 11 km. S of Santiago Chivela; Sarabia (3); Tapanatepec (67); Tehuantepec (66); Tolosita (2); Ubero; Unión Hidalgo; Zanatepec (6).Veracruz: Acayucan (7); Alvarado (3); Amatitlán; Aquilera; Ciudad Alemán (3); 8 km. SW of Coatzacoalcos (9); Cosamaloapan (4); Cosoleacaque (8); 10 km. SE of Hueyapan; Lerdo de Tejada; Novillero (6); Tula (2).

This is the only species of small hylid that crosses the isthmus. Calling males were found in and about ponds on the savannas in southern Veracruz, in ponds in open forest in northern Oaxaca (not in forest pools), and in temporary pools in the scrub forest on the Pacific lowlands. Individuals usually called from bushes and reeds in or at the edge of ponds. The call is a short "braaa." Dates of breeding choruses indicate that by the time the other small species of hylids in the Gulf lowlands reach the peak of theirbreeding season, that ofH. staufferiis essentially over; no large breeding congregations were found in July. On July 8, 1956, two metamorphosing young were found clinging to blades of grass in a pond; they had snout-vent lengths of 8 and 9 mm. and tail stumps less than 3 mm. in length. Others were found on July 13 and 26. The juveniles are nearly unicolor olive green above and white below.

In life the adults vary greatly in color pattern. The dorsal ground color is yellowish tan to olive brown with olive brown or dark brown spots, some of which in certain individuals are connected to form longitudinal dark stripes. On the posterior surface of the thighs are small white flecks. The belly is white, and the vocal sac is a rich yellow. Twenty males have an average snout-vent length of 26.3 mm.; they have no horny nuptial pads. No noticeable differences in either color or body proportions were found between the populations on either side of the isthmus.

Hylella sumichrastiBrocchi

Oaxaca: Cerro Arenal (5); Cerro San Pedro (2); Escurano; La Concepción (41); Portillo Los Nanches (6); San Antonio (16); 11 km. S of Santiago Chivela (18); Santa Lucía (7); Tapanatepec (5); Tehuantepec (8); Tenango (49); Tres Cruces (19).

With the exception of the series from 11 kilometers south of Santiago Chivela, most of these specimens were found in small arboreal bromeliads during the dry season. Males were found along a clear, shallow, rocky stream south of Santiago Chivela on July 6, 1956. The frogs were calling from bushes and rocks in and along the stream. When disturbed, they jumped into the water and floated downstream until they were able to hold onto a rock or other object. The call is a loud "bra-a-ah." In breeding individuals the dorsum is pale yellow; the belly is white, and the vocal sac is yellow. The iris is pale golden yellow. Eighteen males have an average snout-vent length of 25.2 mm. All have dark brown nuptial tuberosities on the pollex.

Certain diagnostic characters of this species as given by Taylor (1943a:50) and Taylor and Smith (1945:598) are in need of revision.Hylella sumichrastihas been characterized as having no vocal sac, rarely having vomerine teeth, and as having a relatively smooth throat. The vocal sac in breeding males is quite evident; it is single, median, and when expanded, spherical. The openings into the vocal sac are narrow slits along the inner posterior border of the jaw rami. Of 151 specimens studied, 74 have vomerineridges between the choanae, and 36 of these have one to three teeth on each ridge. The belly and undersurfaces of the thighs are granular; the throat is only somewhat less so. The granular condition may be correlated with breeding, for specimens obtained from bromeliads in the dry season had rather smooth throats. It seems that the vocal sac atrophys in the non-breeding season. These seasonal changes may account for the diagnoses given by Taylor (op. cit.) and Taylor and Smith (op. cit.); likewise, since many of the specimens obtained by Smith in the dry season were juveniles and subadults, the development of the vomerine ridges could not be diagnosed properly.

The range of this species encompasses the Pacific slopes of the Isthmus of Tehuantepec eastward to the upper Cintalapa Valley and vicinity of Tonalá in western Chiapas. Priscilla Starrett collected tadpoles ofH. sumichrastifrom a stream 19 km. N of Arriaga, Chiapas. These limited observations on the ecology of this frog suggest that it breeds in the fast-moving streams of the Pacific slopes, and that it seeks shelter in arboreal bromeliads during the dry season.

Phrynohyas modestaTaylor and Smith

Oaxaca: Tuxtepec.Veracruz: 20 km. S of Jesús Carranza; 20 km. ENE of Jesús Carranza (2); Minatitlán.

I have not collected this species in the isthmus. The locality records indicate that the range is discontinuous (Duellman, 1956:27). The species occurs on the humid Pacific slopes from south-central Chiapas eastward to El Salvador and on the humid Gulf lowlands from southern Veracruz eastward into Tabasco, but is unknown from the dry Pacific slopes and plains in the isthmus.

The acquisition of several specimens of this species in southern Veracruz, Tabasco, and Oaxaca, together with a knowledge of the variation displayed byPhrynohyas spilomma, suggests thatmodestamay be a color variety ofspilomma.

Phrynohyas spilommaCope

Oaxaca: Tapanatepec (3).Veracruz: Amatitlán (12); Chacaltianguis (2); Ciudad Alemán (6); Cosamaloapan; Novillero (3).

Like the preceding species, this frog is unknown from the arid Pacific lowlands of the isthmus; its presence at Tapanatepec, a locality situated in more mesic conditions than prevail on the Plains of Tehuantepec, indicates that it may have a distribution on the Pacific slopes much like that ofP. modesta. Furthermore, this frogwas not detected in the rainforests of the Gulf lowlands; in that region it was found only in scrub forest and savanna.

On July 26, 1956, numerous choruses of these frogs were heard between Ciudad Alemán and Tlacotalpan, Veracruz. The call is a loud, nasal "grawl" repeated continuously. The males call from the water. Several clasping pairs were found in shallow grassy ponds amidst the scrub forest. The ground color varies from reddish brown to tan with dark brown dorsal markings. The iris is golden, and the vocal sacs are dark olive brown. After a light shower during the dry season, six individuals were found on the low branches of trees at night near Ciudad Alemán.

Phyllomedusa callidryas tayloriFunkhouser

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