TOXOCHELYID^:. 



'65 



are 3 others joined in their natural relation, and 3 more joined together and the hinder- 

 most united with the suprapygals. The single neural must belong in front of all the others. 

 It can not be the first one, because it is too thick in front for the nuchal, in case this was as 

 thin behind as in the genus generally; also because it is not crost by the sulcus separating the 

 first from the second vertebral scute. It can hardly be anything else than the second neural. 

 At the hinder end of the upper surface there is a half-facet for another bone, one of the series 

 of ossicles mentioned above. The neural which is regarded as the third has on its anterior 

 end a half-facet which completes the one on the supposed second neural. Behind this facet 

 is a sulcus, believed to be the one which divides the first from the second vertebral scutes. 

 The fourth neural has no tubercle of its own, but its hinder end supported a small part of 

 the tubercle which belongs to the fifth neural. This tubercle has a length of 20 mm. Behind 

 it is the sulcus which passes between the third and the fourth vertebral scutes. The tubercle 

 is wholly co-ossified with the bones on which it rests, but there are traces of the sutures. The 

 sixth neural is sharp along the midline, while its sides slope steeply, like a high-pitcht roof. 

 The seventh neural is short and closely joined to the eighth. A long and strongly comprest 

 tubercle occupies nearly the whole length of both these neurals and appears to be co-ossified 

 with both, only traces of the sutures remaining. 



The suprapygals are co-ossified. The first is sharply rooft, while the next one has a rather 

 high and comprest tubercle. The anterior suprapygal appears to have been expanded on 



each side, but the expansions are broken away. The sulcus 

 between the fourth and the fifth vertebral scutes doubtless 

 crost behind the tubercle on the second suprapygal. The 

 pygal is represented in plate 30, fig. I . Its height is 14 mm. ; 

 its width from side to side, 27 mm. Its upper, or anterior, 

 border appears to have articulated with a suprapygal which 

 is now missing. The upper surface of the pygal is longitudi- 

 nally grooved, while the inferior has a more extensive longi- 

 tudinal channel. This pygal is quite different from that 

 of the type of T '. stenopora. The dimensions of the neurals 

 and suprapygals are shown in the accompanying table. 



It is evident that there were 1 1 pairs of peripherals, as 

 in most turtles. The two anterior are narrow and thin. These are followed by 4 others which 

 are thicker and broader, and these again by others which are thin. The table gives the 

 dimensions of the peripherals present. The width is taken at the front end. 



The anterior end of the first peripheral is oblique for articulation with the nuchal. The 

 third and the succeeding peripherals to the ninth inclusive have each a pit for a corresponding 

 rib-end. The tenth has no pit. The eleventh is not present. Since the hinder end of the 

 tenth peripheral is 19 mm. wide and the articular end of the pygal only 12 mm. wide, it follows 

 that the eleventh was considerably wider at one end than the other. All the peripherals are 

 crost by shallow sulci. 



Dr. Wieland has represented (Amer. Jour. Sci., xx, 1905, p. 335, fig 6; here reproduced 

 as fig. 229) the rib-end of the eighth costal as entering a pit in the anterior end of the eleventh 



peripheral. The end of the rib was not present and it is 

 stated that the rib-pits are all small. In the specimen 

 figured by Dr. Case (Univ. Geol. Surv. Kans., iv, 1898) 

 the eighth costal comes down to a thin edge and there 

 appears to have been no rib-end. Moreover, Case states 

 that the eleventh peripheral has no groove nor pit for a 

 rib. At my request Dr. C. E. McClung, of the University 

 of Kansas, examined this specimen. He finds the pygal 

 and the eleventh peripheral in their natural positions and 

 the eighth costal with a sharp border and no trace of a 

 rib. Case is probably in error in representing the rib of 

 the seventh costal plate as going to the tenth peripheral. 

 The plastron appears to have resembled quite as much that of the Cheloniidae as it did that 

 of Chelydra. As in the former family, that part of the plastron which lay between the fore and 



