bothremydidjE. 105 



retain the name to which Cope finally referred all the species named above and some others. 

 In his monograph of 1869 and 1870, he described all his species and made Prochomas a 

 subgenus of Taphrosphys. Here T . molops was regarded as the type of Taphrosphys. 



All the species known to belong to this genus are represented by fragmentary individuals, 

 but these furnish us the means of obtaining a pretty clear idea of the structure of the carapace 

 and the plastron. Nothing is known regarding the skull, unless it be that the skull known as 

 Bothremys cooki belongs to a species generically identical with Taphrosphys. Of the limbs 

 extremely little is known. Evidently the genus belonged to the Pleurodira and was not far 

 removed from Podocnemis. There were 8 pairs of costal bones, the last two pairs meeting on 

 the midline. The nuchal bone is large and expanded behind. There were seven neurals, the 

 first large, the last small. There were 1 1 pairs of peripherals, a suprapypal and a pygal. The 

 peripherals of the hinder part of the carapace were thin and acute. Those of the anterior 

 portion of the bridge, the fourth and fifth, appear to have had the free border thickened and 

 rounded or with faces at right angles; while those succeeding them had the free borders acute 

 and the faces, upper and lower, meeting at an angle less than right. 



On the inferior side of the first costal was a deep pit for the reception of the axillary buttress; 

 on the fifth was another pit for the inguinal buttress. An extensive excavation, partly in 

 the seventh costal and partly in the eighth, received the upper end of the ilium. This excava- 

 tion occupied more than a half of the length of these costals. 



The upper surface of the carapacial bones is markt by irregular grooves, which anastomose 

 more or less and divide it into areas differing in size and form in the different species and on 

 different parts of the same individual. The sulci are shallow and sometimes obscure. Evi- 

 dently, the epidermis was thin. There was no nuchal scute. The vertebrals were rather 

 broad. The marginals did not overlap on the costal bones. 



The plastron was well developt, but the anterior lobe was short and broad, and rounded. 

 Strong buttresses rose from the plastron to articulate with the carapace. On the xiphiplastrals 

 were well-developt articulatory surfaces for union with the ischia and the pubes. The posterior 

 notch was large and rounded. As stated by Cope, and as shown by the borders of various 

 hvoplastra and hypoplastra, there were small triangular mesoplastra, which occupied each a 

 position on its_bridge. The free borders of the anterior lobe were mostly obtuse; those of the 

 hinder lobe were mostly acute. The inferior surface is sculptured like the carapace; but 

 often the markings are obscure. The scutes of the anterior lobe are not all satisfactorily 

 determined. There was a large intergular that occupied a considerable part of the entoplastron. 

 Apparently, as shown in the figure of the anterior lobe of T. molops (fig. 1 16), this was bounded 

 in front by a sulcus across the entoplastron, thus permitting the gulars to meet each other at the 

 midline. It is possible that the intergular extends to the front of the lobe, as represented in 

 fig. 106, and that the gulars do not join each other. The numerals lie on the outer ends of the 

 epiplastra, overlapping on the hyoplastra. The arrangement of the other plastral scutes may be 

 seen from the figures. Those on the bridges are not known. 



/'. Species with shell having an even surface, except that it bears a network of vascular grooves. 

 a 1 . Surface of shell usually with a close network of rather broad grooves. 



1. A large species with bones of moderate thickness; the fourth vertebral scute 



nearly a half wider than long sulcatus 



2. A species of moderate size; second and fourth vertebral scutes little wider 



than long longinuchus 



j. A small species with thin bones; second vertebral scute twice as wide as long; 



the fourth probably as wide as the second leslianus 



4. A large species with thick bones; front of plastron broad, truncated, or concave 



on each side of the thickened epiplastral symphysis strenuus 



5. A large species with bones of moderate thickness; front of plastron rounded; 



the first and third vertebral scutes about one-half wider than long molops 



a". Surface with thread-like grooves which form large meshes. 



A large species with thick bones; entoplastron broader than long, its postero- 

 lateral sides excavated dares 



A 2 . Surface of shell coarsely sculptured like that of the Trionychidae nodosus 



