THAI. ASS KMYDID^E. 



149 



have been taken from the plastron of one of the specimens described by him as O. emargmatus. 

 Remarks on this specimen are made under the last-named species. In Cope's figure of the 

 plastron the hyoplastron on the left side of the drawing is placed too horizontally. The anterior 

 outer angle ought to be directed strongly forward. This species resembles 0. borealis. For 

 differences see under the latter species. 



Osteopygis sopitus Leidy. 

 Figs. 181-184. 



Chelone sopita, LEIDY, Smithson. Contrib. Knowl., xiv, 1865, pp. 104, 119. MAACK, Palaeontographica, 



xvin, 1869, pp. 238, 283. , 



Osteopygis sopitus, HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 441 (in part). 



The type specimen of the present species has not hitherto been figured. It belongs to the 

 New Jersey State collection and is at Rutgers College, New Brunswick, New Jersey, where 

 the writer has examined it. This type consisted of 4 peripherals, but Leidy was uncertain 

 whether or not they belonged to one individual. These bones had been obtained in the 

 Cretaceous greensand at Tinton Falls, Monmouth County, New Jersey, probably in the upper 

 bed. Other specimens, which were mentioned by Leidy in his description of this species and 

 figured, were afterwards referred by Cope to Lytoloma angusta, and probably correctly so. 



182,;. 



183. 



FIGS. 181-184. Osteopygis sopitus. Peripheral of type. X-l. 



181. Seventh? peripheral, with section. 



182. Hinder peripheral, with section (1820). The interrupted line of the 



section indicates the depth of the pit. 



183. Hinder peripheral. 



184. Section of a peripheral. 



Other specimens were referred by Cope to Leidy's species. One of these had been 

 secured at Harrisonville, Salem County, New Jersey, in a sort of limestone. This specimen is 

 now in the American Museum of Natural History and has the number 2361. Almost certainly 

 it is not a species of Osteopygis, and it has in the present work been referred provisionally 

 to Rhetechelys platyops (Cope). 



The four peripherals of the type belonged behind the bridges. Figures taken from three 

 of these are here presented. Fig. 181 represents in outline one which is regarded as being the 

 right seventh. It is 1 15 mm. long, 59 mm. wide near the anterior end, 20 mm. thick at this end, 

 and 12 mm. at the posterior end. There are 3 faces an upper, a lower, and an inner, or 

 visceral. The pit for the rib is nearer what is regarded as the hinder end and is somewhat 

 flattened in section. Above the figure is a section taken at the anterior end of the bone. Another 

 peripheral (fig. 182) is about 87 mm. long, 82 mm. wide, 18 mm. thick at one end, 14 mm. at 

 the other. In the visceral face is a pit for the end of a rib. Each diameter of the pit at its 

 opening is 9 mm. The upper face is quite concave from the acute free border to the costal 

 border. Near the figure is a section (1820) taken at the thicker end of this peripheral, which 

 represents the diameter and depth of the rib-pit. Another peripheral, probably a ninth or 

 tenth, has the costal border broken away. The rib-pit is flattened. Figure 183 is a section of 

 this bone. Its greatest thickness is 24 mm. Fig. 184 is a section taken along the transverse 

 sulcus of a fragment representing about one-half of a peripheral. The upper and lower faces 



