DERMATEMYDI I).*;. 



271 



Batrach. Reptilia, Aves N. A., 1869 (1870), p. ii. Hay, Bibliog. and Cat. Foss. Vert. N.A., 1902, 



p. 445; Amer. Jour. Sci. (4), xvm, 1904, p. 265, plate xiii, rigs. 1-3, text-fig. 2; Amer. Geologist, 



\\\\, 1905, p. 331. 



mingensis, Con:, I \r. Batrach., Rtptilia, Aves X. A., 1S70, p. 233; l'roc. Amer. Pliilos. Soc, 



xi, 1870, p. 297. 

 Dermatemyi wyomingensis, Cope, otli Ann. Report U. S. Geol. Surv. Terrs., 1872 (1873), p. 624; Amer. 



Naturalist, XVI, 1XS2, p. 491, fig. 9. 

 Dermatemyi vyomingensis, Cope, Vert. Tert. Form. West, 1884, p. 142. 

 />' . na ponder os a, Con , (>th Ann. Report U. S. Geol. Surv. Terrs, 1872 (1873), p. 624. 

 Ba'enaf ponderosa, Hay, Bibliog. and Cat. Foss. Vert. N. A., 1903, p. 458. 



The type of the present species belongs to the Academy of Natural Sciences at Phila- 

 delphia. The specimen was obtained somewhere in the neighborhood of Fort Bridget, 

 \\ voming, from which locality probably all the known specimens have been derived. The 

 level is therefore that of the lower portions of the Bridger beds. Of the type, some of the 

 peripherals are missing, also the front of the plastron. The total length of the carapace in 

 lite was nearly 450 mm.; the breadth, about 310 mm. On the hinder third of the carapace 

 there is a prominent carina, the summit of which is flat. The anterior neurals are considerable- 

 longer than wide, with the broader end directed forward. The free borders of the anterior 

 peripherals are thickened and obtuse. The surface of the carapace is mostly smooth, but pos- 

 teriorly somewhat corrugated. The dimensions of the vertebral scutes are given in the table. 



The plastron is relatively small, and 

 large spaces are left between it and the 

 carapace, thus favoring the movements 

 of the legs. The anterior lobe is 148 

 mm. wide at the base. The bridge has a 

 width of 105 mm. The hinder lobe ter- 

 minates obtusely behind. The length is 

 94 mm.; the width at the base, 115 mm. 

 On each of the bridges are 3 inframar- 

 ginal scutes. Of these the hindermost 

 extends forward on the hyoplastron. 



Dr. Leidy described a second spec- 

 imen which had been discovered at 

 Church Buttes. This shell was impor- 

 tant because it furnisht the front of the plastron, which Leidy figured in his Contributions 

 (plate xv, fig. 6). This front, however, differs so much from that of all others found since, 

 that there is some reason for suspecting that it belongs to a distinct species, being truncated 

 and notcht in front. Below some details are given regarding this specimen. 



In the Cope collection belonging to the American Museum of Natural History is a large 

 specimen which presents the carapace (plate 40, fig. I ; text-fig. 337): but of the plastron there 

 is only the impression of the hinder lobe on the matrix. The catalog number is 1494. Were 

 it not that Cope describes the form of the anterior lobe, it might be supposed that it is the 

 specimen mentioned by him in the Proceedings of the American Philosophical Society (vol. 

 xi, p. 297). It is possible that that author did not intend to state that his specimen possest 

 this lobe, but referred to what Dr. Leidy had determined. The total length of the carapace is 

 435 mm., in a straight line; the width is 283 mm.; and the height, about 180 mm. The 

 specimen is remarkable for its narrowness. The anterior edge is thickened and rounded like 

 the edge of one's little finger. The thickness of the first peripheral is 16 mm. The hinder 

 free borders are also obtuse, but much thinner, the thickness near the edge of the tenth being 

 7 mm.; but this increases to 14 mm. at halt the height of the bone. The neurals are narrow. 

 The dimensions of the neurals and the \ertebral scutes are presented in the table above. 



There are 12 pairs of marginal scutes. The costo-marginal sulcus runs considerably below 

 the costo-peripheral suture. There appears to be present a ninth pair of costal plates (fig- 337, 

 c.p.? 9). 



The American Museum expedition of 1903 secured 2 specimens of this species at Grizzly 

 Buttes. These have the catalog numbers 5934 and 5967. No. 5967 presents a large portion 



