Fig. 3. Specimen 217. This specimen shows better than any other the form of the gnathites of the cephalon. Note also the setæ of the exopodites under the cheek at the right. The appearance of a hook on the posterior gnathite on the right may be accidental, but it does not show broken edges, × 6.85.
Fig. 4. Specimen 215. The ventral side of the cephalon of a small entire specimen. Shows well the form of some of the gnathites and a few of the endopodites. Note the unusual position of the antennules. × 7.63.
Fig. 5. Specimen 226. This specimen did not photograph well, but is important as showing the exopodites and endopodites emerging from under the cephalon. × about 6.
[171]
PLATE I.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
[172]
[173]
[Pl 2]
PLATE 2.
Photographs ofTriarthrus becki, made by C. E. Beecher.
Fig. 1. Specimen 201. The entire specimen, details of which are shown inpl. 3, fig. 4andpl. 4, figs. 1, 2. The dorsal test has been removed from the anterior segments on the right side. × 4.12.
Fig. 2. Specimen 206. A small individual with the endopodites, and the exopodites minus their setæ; well preserved on the left side. Note the position of the antennules. The course of the facial suture is unusually well shown. × 10.
Fig. 3. Specimen 210. The specimen which served as the main basis for Professor Beecher's first figure of the appendages of the thorax, specimen 206 (fig. 2, this plate) having supplemented it. Note the "normal" position of the antennules and the extension of the appendages from beneath the pleural lobe. Specimens with the antennules in this position may possibly be males. × 4.
Fig. 4. Specimen 205. A small specimen with some of the appendages preserved, especially toward the posterior end, but particularly valuable for the unusually well preserved metastoma. × 11.
Fig. 5. Specimen 211. A small cephalon, cleaned from the ventral side, and showing well the gnathites which approach each other unusually closely on the median line. × 10.5.
Fig. 6. Specimen 219. An entire specimen of medium size, developed from the ventral side. It shows particularly well the "normal" curvature of the antennules, the change in form of the segments of the endopodites from cephalon to pygidium, and, along the axial lobe, the apodemes of the ventral integument. See alsopl. 4, fig. 4. × 3.6.
[175]
PLATE II.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
[176]
[177]
[Pl 3]
PLATE 3.
Photographs ofTriarthrus becki, made by C. E. Beecher.
Fig. 1. Specimen 204. See also textfig. 42andpl. 4, fig. 6. The exopodites and endopodites of the first few segments of this specimen are better preserved than those of any other revealing them from the dorsal side, × 9.5.
Fig. 2. Specimen 220. A large individual exposed from the lower side. It shows well the endopodites and part of the exopodites, and, rather better than any other specimen, the endobases of the coxopodites. × 2.4.
Fig. 3. Specimen 216. A small entire specimen showing considerable of the detail of the appendages of the cephalon, and some of those of the remainder of the body, × 7.4.
Fig. 4. Specimen 201. This figure shows the details of the appendages of the left side and of the pygidium. Note the plate on the median line back of the pygidium, the sockets for spines, and the terminal spines on the anterior endopodites. See alsopl. 2, fig. 1andpl. 4, figs. 1, 2. × 7.1.
Fig. 5. Specimen 207. One half of the posterior part of the thorax and pygidium, showing exopodites and endopodites as seen from the dorsal side, × 7.6.
Fig. 6. Specimen 214. The exopodites have been turned back nearly parallel to the axis of the shell. Notice particularly the long flattened setæ and the spinose spatula-shaped terminal portion of each shaft. See alsopl. 1, fig. 2. × 7.
[179]
PLATE III.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
[180]
[181]
[Pl 4]
PLATE 4.
Photographs ofTriarthrus becki, made by C. E. Beecher.
Fig. 1. Specimen 201. Another photograph, similar tofig. 4, pl. 3, but showing more clearly some details of spines on the endopodites. × 12.66.
Fig. 2. Specimen 201. Three appendages on the right side of the thorax. See alsopl. 2, fig. 1andpl. 3, fig. 4. × 12.66.
Fig. 3. Specimen 223. A small crushed specimen which nevertheless shows well the appendages of the right side of the thorax, developed from the ventral side. Note coxopodites, exopodites, and endopodites, and that all appendages are moved equally laterally from their original position. × 11.4.
Fig. 4. Specimen 219. Another photograph, with different lighting, of the individual shown inpl. 2, fig. 6. This print brings out better the coxopodites and the folds of the ventral membrane. × 3.23.
Fig. 5. Specimen 222. This specimen is interesting, because it shows the endopodites in what is probably their natural position, that is, in a plane nearly vertical to the plane of the body, instead of being flattened down, as is usually the case. The appendages under the pygidium are unusually well preserved. × 12.
Fig. 6. Specimen 204. Photograph of the entire specimen of which a part is shown in textfig. 42andpl. 3, fig. 1. × 4.5.
[183]
PLATE IV.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
[186]
[185]
[Pl 5]
PLATE 5.
Photographs ofTriarthrus becki, made by C. E. Beecher.
Fig. 1. Specimen 209. Photograph of the pygidium shown inpl. 6, fig. 2. This specimen shows especially well the way in which the exopodites of the pygidium decrease in length backward, × 11.5.
Fig. 2. Specimen 229. The under side of the posterior end of a medium-sized specimen, showing the appendages, especially the endopodites. On and among the limbs are scattered numerous minute spheres of pyrite, of the kind usually known as "trilobite eggs." They do not show very well in the photograph, but can be made out much more clearly with a hand lens, × 12.
Fig. 3. Specimen 230. A specimen showing the appendages of the posterior part of the thorax and the pygidium. The same individual is also shown in textfig. 44. Note particularly the form of the segments of the endopodites, and the spines on them, × 13.
Fig. 4. Specimen 227. The small doubly curved bodies shown in this figure lie under the axial portion of the cephalon and anterior part of the thorax. The specimen still has a very thin coating of matrix between it and the shell. Whether the curved bodies have anything to do with the trilobite is not known, × about 12.
Fig. 5. Specimen 221. A small individual which shows well the exopodites of the posterior part of the thorax. Note the spatulate terminations and the spines of the shaft, × 11.
Fig. 6. Specimen 202. Posterior part of the thorax and pygidium, showing endopodites and exopodites projecting under the dorsal test. Note the spiniferous plate on the median line, and the large opening in the anterior portion of it. × 9.75
[187]
PLATE V.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
[188]
[189]
[Pl 60]
PLATE 6.
All figures except 4 and 5, from photographs by C. E. Beecher.
Fig. 1.Triarthrus becki. Specimen 203. A well preserved small individual, showing the appendages of the right side of the thorax. × 11.46.
Fig. 2.Triarthrus becki. Specimen 209. A well preserved individual, showing the antennules and some appendages of thorax and pygidium. For detail of the pygidium, seepl. 5, fig. 1. × 4.
Fig. 3.Triarthrus becki. Specimen 218. Ventral side of the pygidium and greater part of the thorax of an individual of medium size. Note especially the relation of exopodites to endopodites of the last two thoracic segments. A drawing of these appendages is shown on textfig. 43. × 4,3.
Figs. 4 and 5. Endopodites, probably from a species ofCalymene. These specimens, with several others, are on a small slab of limestone from the Point Pleasant (Trenton) beds opposite Cincinnati, Ohio. Specimen in the U. S. National Museum. Photographs by R. S. Bassler.
Fig. 6.Acidaspis trentonensisWalcott. Both the specimen, No. 245, and the photograph are poor, but show that in this genus the endopodites are like those of Triarthrus. × 8.5.
Fig. 7.Cryptolithus tessellatusGreen. Specimen 234. This specimen shows well the backward directed antennules and also the outer segments of some of the cephalic endopodites. × 11.
PLATE VI.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
PLATE 7.
Photographs ofCryptolithus tessellatusGreen, made by C. E. Beecher.
Fig. 1. Specimen 233. The best preserved individual, the one from which Professor Beecher's drawing (text fig. 45) was made, and which served as the principal basis for the restoration (text fig. 20). Note the long, backward directed antennules, the abrupt backward turn of the outer portions of the endopodites, the way in which the exopodites extend beyond the endopodites, and the fact that alt are beneath the cover of the dorsal shield. The hypostoma is turned entirely around. × 10.9.
Fig. 2. Specimen 235. Half of the thorax and pygidium, with the appendages revealed from the ventral side. Note the abrupt manner in which the outer portions of the endopodites are turned backward. See alsopl. 8, fig. 3, andpl. 9, fig. 1(right half). × 14.45.
Fig. 3. Specimen 236. Detail from fig. 4, to show the blade-like setæ of the exopodites and the numerous terminal spines of the endopodites. × 30.
Fig. 4. Specimen 236. The appendages of the thorax and pygidium, seen from the lower side. Specimen 236 is the right half of the same individual from which specimen 235 was obtained. Note the interarticular membranes between the segments of the endopodites and the blade-like setæ of the exopodites. See alsopl. 9, fig. 1(left side). × 19.
Fig. 5. Specimen 236. The same specimen, seen from the dorsal side, showing, when the test is removed, the long blade-like setæ of the exopodites. See alsopl. 9, fig. 2(right half). × 19.
PLATE VII.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
PLATE 8.
Photographs ofCryptolithus tessellatusGreen, made by C. E. Beecher.
Fig. 1. Specimen 231. A nearly complete individual, cleaned from the ventral side and showing obscurely the hypostoma and fragments of numerous appendages. Note the lines of appendifers along the sides of the axial lobe. × 11.
Fig. 2. Specimen 232. Although this is not very well preserved, it shows more of the cephalic appendages than any other. Even so, only just enough is shown to indicate that they were similar to those on the thorax. × 12.
Fig. 3. Specimen 235. Dorsal side of the appendages of the thorax and pygidium. Seepl. 7, fig. 2for the ventral view. Onpl. 9, fig. 2(left side) is a drawing taken from the same specimen. × 11.
Fig. 4. Specimen 238. Part of a thorax and pygidium, seen from the ventral side. The series of heavy segments shown in the upper part do not belong to one appendage, but are the distal ends of several endopodites. See also textfig. 46for a drawing of this specimen. × 18.
Fig. 5. Specimen 237. Pygidium and part of the thorax, with some of the appendages. × 11.
PLATE VIII.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
PLATE 9.
Cryptolithus tessellatusGreen. Upper drawing by C. E. Beecher; lower drawing by Miss F. E. Isham, under the direction of C. E. Beecher.
Fig. 1. Appendages of the thorax and pygidium, seen from the ventral side. These are not restorations, but drawings from the halved individual numbered 236 (right side of drawing) and 235. For photographs of these specimens, seepl. 7, figs. 2, 4. × 20.
Fig. 2. Appendages of the thorax and pygidium, seen from the dorsal side. Same specimen as in fig. 1. For photographs, seepl. 7, fig. 5, andpl. 8, fig. 3. × 20.
PLATE IX.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
PLATE 10.
From photographs made by C. E. Beecher.
Fig. 1.Isotelus latusRaymond. Ventral surface of the specimen in the Victoria Memorial Museum at Ottawa, Canada. Note the large, club-shaped coxopodites and the more slender endopodites. The first large coxopodite back of the hypostoma belongs to the last pair of cephalic appendages. The coxopodite of the appendage in front of it is seen turning in beneath the tip of the hypostoma. × 2.
Fig. 2.Isotelus maximusLocke. The ventral side of the specimen described by Mickleborough and now in the U. S. National Museum. The tips of the hypostoma may be seen at the front, and the first two pairs of coxopodites behind them belong to the last two pairs of appendages of the cephalon. Note how much stronger the coxopodites are than the endopodites. The appendages of the pygidium show but poorly, × 1.45.
PLATE X.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON
PLATE 11.
Ceraurus pleurexanthemusGreen. A restoration of the ventral surface and appendages, made by Doctor Elvira Wood, under the supervision of the writer, from data obtained from the translucent slices prepared and described by Doctor Walcott. × 5.
PLATE XI.
HELIOTYPE CO. BOSTON
HELIOTYPE CO. BOSTON