TRIONYCHID. Sly 
sutural edge on one side. At the junction of the sutural border with the free border, the thick- 
ness is 10 mm. On the sutural border, at the end of the fragment toward the midline, the 
thickness is reduced to 8 mm.; that is, this costal is thicker at the outer end than nearer the 
midline. This and other fragments show that the free edge, on each side of the rib extension, 
was cut off at nearly right angles with the sculptured surface. The sculpture came down close 
to the distal ends of the costal plates. In some cases, but not all, there is a tendency for the 
pits to arrange themselves, at the ends of the costals, somewhat parallel with the free border 
of the bone. 
Fig. 5 (fig. g of Cope) is a portion of the costal plate of a small individual. The width is 
21 mm.; the thickness, only 4mm. Fig. 6 (fg. 8 of Cope) represents a fragment from prob- 
ably the proximal end of a costal plate. Here the ornamentation consists of tubercles and 
short, winding, and occasionally anastomosing, ridges, the pattern being somewhat coarser 
than that of the plastron, there being two furrows or pits in about 5 mm. This is true of most 
of the ornamentation of the carapace. 
Amyda radula (Cope). 
Plate 86, figs. 11, 12. 
Trionyx radulus, CoPE, Systematic Cat. Vert. Eocene New Mexico, 1875, p. 35; Report on Geol. 
N. W. N. Mex., in Appendix Ann. Rep. Chief of Engineers, 1875, p- 1015 (of separata, p. 95); 
Wheeler’s Surv. W. tooth Merid., 1v, 1877, p. 45, plate xxvi, figs. 11-16.—Hay, Bibliog. and Cat. 
Foss. Vert. N. A., 1902, p. 454- 
In his original description Professor Cope characterized with great brevity this species of 
Amyda. In his final report on his explorations in New Mexico, publisht in the fourth volume 
of the Wheeler Survey, he gave some additional data and figures of some of the fragments on 
which he had based the species. Even here, however, the description is limited to 10 lines of 
print. The type specimens are now in the U. S. National Museum, at Washington, No. 2581. 
They were collected in Wasatch deposits along the Gallinas River, New Mexico. 
The figures given by Professor Cope make the summits of the ridges surrounding the pits 
appear too broad. They are really narrow. From their summits the walls slope rapidly to the 
bottoms of the pits, but not so abruptly as the figures indicate. 
Cope’s fig. 11 represents the distal end of a costal. It has a thickness of 6 mm. In the 
original of fig. 13 the free border, at the side of the extension of the rib, is cut off nearly square, 
with a tendency of the upper layer to overhang. It will be observed that the sculpture of this 
and of the costal of his fig. 14 (plate 86, fig. 11) comes down close to the free border of the bones. 
Cope’s fig. 15 (plate 86, fig. 12) represents the middle of a costal. The sutural border is 4 mm. 
thick. There are 6 pits ina line 20 mm. long. His fig. 16 1s that of a neural which has a thick- 
ness of 6 mm.; and there are 5 pits in a line 15 mm. long. In these specimens the rib does 
not stand out prominently on the under side of the costal. 
Cope (Vert. Tert. Form. West, p. 119) identified with this species some portions of a 
carapace found in the Bridger beds. This is here described under Amyda equa. For a 
discussion of the relationships of the Wasatch species and the closely related 4. equa of the 
Bridger see under the latter. It is greatly to be desired that additional materials of 4. radula 
from the type locality shall soon be discovered and described. 
A. radula has the sculpture similar to that of 4. cariosa. The two appear to be distin- 
guisht by the greater thickness of the shell of the latter and the groove around its free margin. 
Amyda equa sp. nov. 
Plate 99, figs. 1-3; text-figs. 672, 673. 
Trionyx radulus, Cope, Vert. Tert. Form. West, 1884, p. 119. 
Amyda radulus, Hay, Amer. Geologist, XXXV, 1905, P- 3 30. 
In the work above cited Professor Cope described and referred to his Trionyx radulus, of 
the Wasatch of New Mexico, some remains of a trionychid which he found in the Bridger beds 
of Wyoming. This Bridger individual now belongs to the American Museum of Natural 
History and has the number 1052. 
