512 FOSSIL TURTLES OF NORTH AMERICA. 



Amyda? prisca Leidy. 

 Plate 97, figs. 2-6. 



Trionyx priscus, Leidy, Proc. Acad. Nat. Sci. Phila. 1851 , p. 329; Smithson. Cont. Knowl., XIV, 1869, 

 art. vi, pp. 115, 120, plate xviii, fig. 9. Cope, Cook's Geol. N. J., 1868, (1869), p. 735; Proc. Acad. 

 Nat. Sci. Phila. 1869, p. 12; Trans. Amer. Philos. Soc, xiv, 1869, pp. 151, 153; Vert. Cret. 

 Form. West, 1875, p. 260. Maack, Pala;ontogr., xvm, 1869, p. 281. Hay, Bibliog. and Cat. 

 Foss. Vert. N. A., 1902, p. 454. 



The original description ot this species given by Dr. Leidy was exceedingly brief, present- 

 ing merely the thickness of the fragment of costal plate on which the species was founded, 

 and the statement that it was derived from the Cretaceous greensand of New jersey. 

 Cope's first mention ot it, cited above, gives only the name; the second a description included 

 in two lines; the third, the name and the information that it came from the greensand of New 

 Jersey; the fourth, that it was derived from the greensand No. 4, by which he meant the 

 equivalent of the Pierre beds of the West. 



Maack merely refers to the species and says that it was the only form of Trionyx then 

 known from the Cretaceous. 



In 1869 Dr. Leidy, as cited above, gave a detailed description and a figure of a character- 

 istic specimen. This specimen must be regarded as the type. It was found in the marl on the 

 farm of G. C. Schenck, in Monmouth County, New Jersey, and was sent to Dr. Leidy by 

 Professor Cook, then state geologist of that state. This type is now in the state collection at 

 Rutgers College, New Brunswick, New Jersey, where it has been examined by the writer. 

 Leidy's figure of the specimen is reverst, but otherwise correct. The pits are abruptly 

 sunken and the ridges are flat. Pits and ridges are both smaller as the free border is approacht. 

 In the middle ot the length of the fragment there are 4 ridges in a line 16 mm. long. 



Professor Cope states (Trans. Amer. Philos. Soc, xiv, p. 152) that the costal plate men- 

 tioned by Leidy as coming from the greensand of Burlington County, New jersey, and now 

 in the collection of the Academy at Philadelphia, belongs to A . halophila (Cope). 



In the Cope collection of reptiles at the American Museum of Natural History there are 

 about a dozen fragments of the carapace, 2 or 3 of the plastron, the distal end of the left 

 humerus, and a posterior dorsal vertebral centrum. These specimens are credited to Dr. C. 

 Schenck, Marlboro, Monmouth County, New jersey, probably the collector of Leidy's 

 specimens. The number of the lot is 2401, and it is probable that it represents more than one 

 individual. These fragments were identified and labeled by Cope as Trionyx priscus. Figures 

 of some of these parts are here presented. Fig. 2, plate 97", represents the upper end of a 

 costal plate, the portion in immediate contact with the neural plate being broken off. The 

 width at the middle of the piece is 28 mm.; the thickness at the sutural border is 7 mm.; and 

 that thru the middle of the width is 8 mm. Fig. 3 of the same plate shows the distal end of a 

 costal bone, but no sutural edge is retained. The thickness near one sutural border is 7 mm., 

 while thru the elevation produced by the rib the thickness is 11 mm. The rib projected 

 beyond the border of the costal plate, but how far can not be determined. The free edge of 

 the costal plate is abruptly rounded off in section. The fragment resembles greatly the border 

 portion figured by Leidy, and this author's figure shows that the rib projected nearly 20 mm. 

 beyond the costal plate. Leidy regarded the costal which he figured as belonging to the left 

 side, but it seems rather to belong to the right. Fig. 4 of the plate referred to appears to be a 

 portion ot the nuchal; but if so, this fragment did not extend to the midline nor show the 

 distal end of the bone. It indicates that there was a median excavation in the front of the 

 carapace, and a fontanel between the nuchal and the first costal plate. The bone is only 5 mm. 

 thick, while in front of the sculptured surface there is a smooth band. Fig. 5 of the plate 

 represents what appears to be the distal end of the hindermost costal plate of the right side. 

 The sutural border is present in front. The projecting rib is broken off just after leaving the 

 plate. 1 he bone is 8 mm. thick and the free edge is cut off rather abruptly in section. Fig. 6 

 is a portion of one costal, probably from the middle of the length. The shorter of the two 

 longer borders shows the suture. 



The two fragments of the plastron afford but little light regarding its structure. It 

 appears to have been 11 mm. thick where the hyoplastron and hvpoplastron are constricted 

 between the legs ot the animal. 



