TRIONYCHIDZ. 521 
The xiphiplastra are missing; but the notches in the right hypoplastron show that these 
bones were articulated as in Platypeltis. 
Three cervical vertebra were exposed in preparing the plastron, the sixth, seventh, and 
eighth. All of these are turned backward, as if the head had been retracted within the shell. 
The sixth has a length of 75 mm. The structure of these vertebra resembles that of P. jerox. 
There is present also one ilium, but there appears to be nothing distinctive about it. 
This species is very distinct from Aspideretes guttatus, but it might be very difficult 
to distinguish small fragments of the two. The last- named species has a much more elongated 
shell and a preneural, ee ecicie which readily distinguish it from Amyda uintaénsis. Rion 
Amyda egregia, which has similar ornamentation, it is distinguisht by the different form of 
the carapace and of the first neural; by the narrower neunale: and by the presence of 6 
instead of 7, of them. 
’ 
Amyda scutumantiquum Cope. 
Plate 100, figs. 2-4; plate 1or, fig. 1; text-figs. 676, 677. 
Trionyx scutumantiquum, Cope, 6th Ann. Report U. S. Geol. Surv. Terrs., i (087 3), p- 617; Amer. 
Naturalist, xv1, 1882, p- 988, fig. 6; Vert. Tert. Form. West, 1884, pp. 118, 121, 
I, ta.—Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 454. 
Amyda acacananiauln Hay, Amer. Geologist, XxXv, 1905, p. 33 
plate xvi, figs. 
The type of this species consists of a nearly complete carapace and a considerable part of 
the plastron, which were found in the Bridger beds, on Cottonwood Creek, in Wyoming. This 
specimen is now in the American Museum of Natural History and has the number 1035. 
Fics. 676 AND 677.—Amyda Scutumantiquum. 
676. Carapace. 
677. Plastron. Restored mostly from left half, 
partly from right. 
Professor Cope also referred to the same species, with some doubt, fragments which had been 
collected from the Wasatch deposits near Black Butte, Wyoming, and! from the same forma- 
tion on Bear River. Where these Wasatch specimens now are the present writer does not 
know. 
On the page facing plate xvi of the Vertebrata of the Tertiary Formations of the West, 
Professor Cope states dhat his figures of this species are reduced to one-fourth the size of nature; 
but this is an error, the figures being almost exactly one-third the natural size. 
This species attained a large size and possest a heavy shell. The length of the carapace 
(plate 101, fig. 1; text-fig. 676) of the type is 430 mm., measuring from the anterior portion 
of the nuchal. The width is very close to 400 mm. There was probably a broad but very 
