THALASSEMYDID^. 163 



Its food has been supposed to have been hard-shelled animals, such as mollusks, which were 

 crusht between its mill-stone-like jaws. The possession of a hookt beak like that of the 

 alligator-snapper suggests, however, that the animal may have been accustomed to the captur- 

 ing of a more active prey, such perhaps as fishes. 



Cope, as cited in the synonymy above, referred certain bones obtained at Harrisonville, 

 Salem County, New Jersey, to Propleura sopita. These consisted, as he says, of 2 peripheral 

 bones, part of a costal, half a femur, and 2 phalanges. This lot is in the American Museum and 

 is found to include three peripherals, a fragment of a costal, and the distal end of a femur. 

 The foot bones are missing. The number is 2361. These bones quite certainly do not belong 

 to Osteopygis. In all specimens known to belong to the latter genus the pit for the rib-end is 

 placed at the middle of the length of the peripheral or not far behind it. Only in the tenth 

 peripheral is it placed close to the hinder end of the peripheral. In the bones of the Harrison- 

 ville specimen the pit is placed far backward. Since Rhetechelys platyops was found in the 

 same limestone not many miles distant, the bones found at Harrisonville are referred provis- 

 ionally to the species just named. 



One of the peripherals appears to be the left first. Its length is 85 mm.; its height 48 mm.; 

 the thickness of the obtuse free border, 19 mm. in front. The articulation with the first costal 

 was not strong and apparently only along the anterior end of the bone. It is not certain that 

 any part of the first vertebral scute descended on this peripheral. Another peripheral is prob- 

 ably the left fifth. The anterior end is broken off, but the length must have been about 1 10 mm. 

 From the hinder end to the intermarginal sulcus is 60 mm. The height of the upper face, at 

 the sulcus, is 62 mm.; the lower face, 53 mm.; the inner face, 50 mm. The pit is in the hinder 

 third of the bone. The upper face is slightly concave; the lower slightly convex; the inner 

 concave. The remaining peripheral is probably the seventh. Cope regarded it as the eighth. 

 Most of the outer border is broken away. The length is 95 mm.; the height, 79 mm.; the 

 thickness of the costal border, 28 mm. in front, 24 mm. behind. The upper surface is some- 

 what concave; the lower, convex; The circular rib-pit is almost wholly in the hinder third 

 of the inner face. The piece of costal is 7 mm. thick at the sutural border. All these bones 

 are smooth, but markt by vascular grooves. The width of the femur at the distal end is 45 

 mm. The diameter of the shaft is 19 mm. The bone was considerably bent. 



Family TOXOCHELYID^ Baur. 



Skull somewhat deprest. Temporal region extensively rooft. Quadrate notcht for the 

 columella. Choanae situated well forward; not underfloored by the palatines. Palatines 

 extending forward to the vomers and forming the outer boundaries of the choanae. Carapace 

 with eleven pairs of peripherals, in addition to the nuchal and pygal. Nuchal not furnisht with 

 costiform processes. Epidermal shields present. Plastron loosely articulated with the carapace, 

 not extending forward to the third peripheral and backward hardly to the eighth. Fore foot 

 with at least 2 claws; the phalanges furnisht with condyles; the limb as a whole resembling 

 that of the Trionychidae. 



Genera 2, Toxochefys and Porthochelys. With these may be included provisionally the 

 insufficiently known genus Cynocercus. 



The writer excludes the members of this family from the Cheloniidae especially because the 

 fore limb had not yet become developt into a flipper like that of the modern sea-turtles. The 

 humerus offers scarcely an approach to that of the sea-turtles. Nor was the hinder limb 

 nearly so much reduced as in the latter. The limbs were probably greatly like those of the 

 Trionychidae. That the anterior limbs were not habitually employed in swimming appears to be 

 shown by the fact that the shell was not excavated over these limbs as it is in the Cheloniidae. 



Genus TOXOCHELYS Cope. 



Skull longer than broad. No nasal bones. Carapace with large lateral fontanels. None 

 of the peripherals in contact with the disk of the carapace. Midline with prominent canna 

 rising at intervals into tubercles, some of which are distinct bones. Tail with a series o 

 comprest tubercles above. Plastron with median and lateral fontanels. 



Type: Toxochelys latiremts Cope. 



