512 FOSSIL TURTLES OF NORTH AMERICA. 
Amyda? prisca Leidy. 
Plate 97, figs. 2-6. 
Trionyx prise us, Lery, Proc. Acad. Nat. Sci. Phila. 1851, p. 329; Smithson. Cont. Knowl., xiv, 1869, 
art. Vi, pp- 113, 120, plate xviii, fig. g.—Copr, Cook’s Geol. N. J., 1868, (1869), p. 7355 Proc. Acad. 
Nat. Sci. Phila. 1869, p. 12; Trans. Amer. Philos. Soc., XIv, 1860, pp: 15251533 Vert-1Cret: 
Form. West, 1875, p. 260.—Maack, Palewontogr., XVIII, 1869, p- 281.—Hay, Bibliog. and Cat. 
Foss. Vert. N. A., 1902, p. 454. 
The original description of 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 of 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 of the length of the fragment there are 4 ridges in a line 16 mm. long. 
Professor Cope states (Trans. Amer. Philos. Soc., X1v, p. 152) that the costal plate men- 
tioned by Leidy as coming from the greensand of Baie 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 1s 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 mb 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 sie costal plate. Leidy regarded ae 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 of 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. The 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 hypoplastron are constricted 
between the legs of the animal. 
