TRIONYCHID#. 51g 
the pits are broad and rounded. The pits measure as in the Opal specimens. Usually 
there are 5 of them in a line 20 mm. long, but sometimes as many as 6 and again as few as 4. 
The thickness of the second neural is 8 mm.; that of the sutural border of the second costal, 
near the distal end, 7 mm.; that thru 
the middle of the width of the same 
oe costal, 13 mm. 
Too little is known regarding Cope’s 
Trionyx radulus, originally found in 
the Wasatch beds of New Mexico, to 
identify the Bridger specimens as the 
same. Inthe Wasatch specimens the 
smooth beveled band around the free 
border is much narrower than in the 
Bridger carapaces, the ridges of the 
sculpturing coming down in places close 
to the edge. In the case of the costal of 
Cope’s fig. 13 the border near the pro- 
jecting rib is cut off nearly square, with 
a tendency of the upper layer to over- 
hang. Nothing of this sort is seen in 
any of the Bridger specimens. ‘The 
costals and the neurals of the Bridger 
forms appear to be thicker than those 
of the type of 4. radula. The pits of 
the latter, too, are smaller, there being 
usually 6 1n a 20 mm. line, instead of 5. 
The ribs of 4. radula do not stand out 
so prominently on the under side of the 
costals as they do in the specimens of 
672. 673. 
Fics. 672 AND 673.—A myda equa. Carapace of type. X 5. 
A. equa. 
672. Carapace. The specimen (plate 99) belonging 
673. Vises of carapace, seen from below. c.p. 2, ¢-p. 8, mb-heads to the U. S. National Museum is taken 
of second, and eighth costal plates; dor.v. 2, dorzv. 8, second 
and eighth dorsal vertebra; nu.p., nuchal plate. as the type of A. equa. 
Amyda uintaénsis (Leidy). 
Plate 100, fig. 1; text-figs, 674, 675- 
Trionyx uintaénsis, LEIDY, Proc. Acad. Nat. Sci. Phila. 1872, p. 267; Contrib. Ext. Vert. Fauna West. 
Terrs., 1873, pp. 178, 342, plate xxix, fig. 1—Copr, Vert. Tert. Form. West. 1884, p. 118; Contrib. 
Canad. Paleont., m1, 1891, p. 5—Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 454- 
Amyda uintaénsis, Hay, Amer. Geologist, XXXv, 1905, p. 330. 
The present species was based on a nearly complete carapace which was procured by Dr. 
Leidy during his stay at Fort Bridger, in the year 1872. It was found, it is stated, in the 
Bridger deposits, at Dry Creek, about 10 miles from Fort Bridger. It is probable that Little 
Dry Creek was meant. If so, the level is B. This specimen belongs to the Academy of Natural 
Sciences of Philadelphia, where the writer has been permitted 
to study it. Originally little more than fragments were missing 
Neural. Length. Width. . . : i ‘ 
from the right side, altho the left side was more damaged. 
I 58 33 Now, however, it lacks the nuchal, which was originally present. 
ss fe oe The specimen was kindly loaned to the writer with permission to 
4 42 21 develop it further, and the result has been to find present most of 
5 38 ) the plastron and some of the cervical vertebra. 
sod at | 
The carapace (fig. 674) is nearly as broad as long, broadest 
somewhat behind the middle of the length, very slightly concave 
in outline near the middle of the front, sinuous along the sides, and truncated behind. As 
stated by Dr. Leidy, the carapace 1s about as convex as that of Platypeltis mutica. The length 
