516 FOSSIL TURTLES OF NORTH AMERICA. 
As regards the thickness, Cope states that one costal was 7 mm. thick at the proximal end, 
and that others were 11 mm. and 12 mm. thick at the middle of the length and at the distal 
ends. At the free margins of the costals the upper layer of bone projected far beyond the lower 
layers, causing, as Cope states, a deep longitudinal grooving of the free border of the carapace. 
The costals had a width of about 45 mm. at the proximal end and of about 60 mm. at the 
distal end. In Cope’s figures the width of the ndges is exaggerated and the pits are made to 
appear too abruptly sunken. 
The figures publisht by Cope show that there are on the proximal ends of the costals 
deeply imprest and irregularly arranged pits, of which there are four or five in a line 20 mm. 
long. Along the sutural borders of each of the costals there is a smooth strip. More distally 
the pits arrange themselves in irregular rows, and sometimes coalesce to form furrows, which 
run parallel with the margin of the carapace. Of these there are about three in 20 mm. In 
Cope’s fgure 7 the ridges and furrows are not represented with enough distinctness. On the 
neurals there was a honeycomb of pits similar to those on the adjacent ends of the costals. 
Cope says that the hypoplastron in his possession presented a rather irregular reticulate 
sculpture medially. The element fgured as a probable xiphiplastron had a "patch of large 
pits; but this bone is really the left extremity of the nuchal. The figure is inverted. The right 
extremity of the nuchal is present likewise. 
Fig. g, plate 86, reproduced from Cope, gives a view, natural size, of a portion of a neural 
bone, while fig. 10 of same plate shows a fragment of a costal plate. 
A. radula has a style of ornamentation quite similar to that of the present species; but 
the shell is thinner, and the free margins are beveled off, instead of having the upper layer of 
bone overhanging the lower layers. 
Amyda? ventricosa (Cope). 
Plate 98, figs. 1-6. 
Trionyx ventricosus, Corr, Extinct Vert. New Mexico, in Wheeler’s Sury. W. rooth Merid., tv, 1877, 
p- 45; plate Ixiv, figs. 7-13; Vert. Tert. Form. West, 1884, pp. 118, 188.—Hay, Bibliog. and 
Cat. Foss. Vert. N. A., 1902, p. 455. 
This species is represented by somewhat more than 25 fragments, which Cope states belong 
to 3 individuals. Of these fragments, 7 are fgured in Cope’s work in the Wheeler Survey, as 
cited above. All these specimens belong to the U.S. National Museum and bear the number 
1112. Of the pieces hgured by Cope, all are present, except the one which furnisht fig. 10 of 
the plate cited. New figures of these are here furnisht, except of the missing fragment. 
This species was ee by Cope in the year 1874, in the Wasatch deposits of Ric Arriba 
County, New Mexico. 
Fig. 1 of plate 98 (Cope’s fig. 13) represents the distal end of the left hypoplastron. This 
bone indicates that the width of the hypoplastron at the narrowest portion was 20 mm., and 
that the various dimensions of at least the distal end of the bone were about as they are in 
Platypeltis sprntfera. Cope states that the ‘‘twin gomphosial processes’’ were short and stout 
but these are not figured, and probably were not present on any of the specimens when found. 
The processes neferred to separated from each other before they left the edge of the “‘cal- 
losities,” and poe were probably short. The thickness of the bone where these processes 
part is 10 mm.; at the sutural edge for union with the hyoplastron the thickness is 7 mm. The 
ornamentation consists of narrow ridges which, near the free border of the bone, curve around 
mostly parallel with these free borders; elsew here, they are irregular in their course. These 
ridges are frequently connected by cross-ridges, and the intery ening spaces form pits and short 
furrows wider than the ridges, Usually there are 2 or 3 pits in a space of about 5 mm. 
Fig. 2 of plate 98 (hg. 12 of Cope) presents the same part as the previous figure, but of 
another individual; but it offers no peculiar features. The same bone of a third individual 
was larger, the thickness at the base of the twin processes being 14 mm. Fig. 3 of the same 
plate (hg. 11 of Cope) is a fragment undetermined as to position, but probably belonging to 
the plastron. It is about 7 mm. thick. The ridges and pits of the sculpture have no regular 
arrangement, and the sculpture turns over the edge just below the outstanding process on one 
side. Fig. 4, plate 98 (fg. 7 of Cope), shows the distal end of a costal plate, including the 
