394 FOSSIL TURTLES OF NORTH AMERICA. 
Cope regarded these turtles as belonging to Stylemys nebrascensis, the common species of 
the White Rives beds of South Dakota. A study of these shells and a careful comparison of 
them with the South Dakota form has convinced the writer that they are specifically different 
and, moreover, belong to two distinct species, one of which 1s the present, the other S. capax. 
The only injury that the type specimen suffered during fossilization is a slight lateral 
compression and a moderate thrusting of the plastron upward toward the carapace. The total 
length of the carapace (plate 64, fg. 1; text-fg. 500) in a straight line is 415 mm.; the width 
of the shell is 215 mm.; the present height is 170 mm. ‘The original width may have been as 
much as 300 mm.; the height as much as 180 mm. These estimates would make the width of 
the shell about 72 per cent. of the length. The carapace is high and convex both longitudinally 
and transversely. Over the bridges the sides were perpendicular or nearly so. There was 
little or no flare to the anterior and posterior peripherals. In outline, both the front and 
hinder ends are broadly rounded. Where the sulci crost the free border the latter is mucronated. 
The nuchal bone is 65 mm. wide along the free border, posteriorly expanding to g5 mm. 
The first neural is elongated and oval. ihe second is octagonal; the third is nearly square; 
the others, hexagonal and mostly with the shorter sides in on The anterior py gal i is bifur- 
cated. The one behind it is four-sided, its hinder border fitting in a notch in the pygal. The 
latter bone is somewhat incurved, and is 51 mm. wide and 50 mm. long on the midline. 
The costal plates are alternately wide and narrow, having 
nearly as high a degree of differentiation as those of the genus 
Testudo. The accompanying table presents the widths of the 
Costal. Upper end. Lower end. 
2 30 68 upper and the lower ends. 
3 a oe The first and second peripherals have a width of 60 mm. 
4 35 72 5 : = < 
5 38 22 along the free border; their extent backward from this border 
: i. - is 57 mm. The eighth is 70 mm. high and 47 mm. wide. All 
/ ml 4 
the free peripherals, as well as the nuchal and the pygal, come 
down to an acute free edge. An obscure carina crosses the 
bridge peripherals from the free border of the anterior to the free border of the posterior 
peripheral. 
The nuchal scute is 27 mm. long and 16 mm. wide. The first vertebral is 126 mm. wide 
in front. The second and third are about 83 mm. wide; the fourth, 72 mm.; the fifth, 110 mm. 
wide posteriorly. On the anterior peripherals the sulci between the marginal scutes and the 
costals fall considerably below the sutures between the peripheral and costal bones. On the 
sides and posteriorly the sulci are little below the sutures; on the posterior suprapygal, above 
the suture. 
The plastron (plate 64, fig. 2; text-fig. 501) has a total length of 360 mm. Its general 
form is as in S. nebrascensis. The anterior lobe has a length of 120 mm. and a width of 166 
mm. at the base. It did not project beyond the front of the carapace. The front of the lip 
falls within the general curve of the lobe. The lower surface of the lip 1s flat, while the upper 
surface curves down to meet it. In §. nebrascensrs the upper and the lower surfaces are about 
equally convex. The entoplastron has the form that it has in S. nebrascensis. The bridge 
has a width of 150 mm. 
The posterior lobe is 105 mm. long and 180 mm. wide at the base. The notch in the 
posterior border is somewhat larger than is usual in S. nebrascensis. As to the thickness of the 
bone, the sloping lateral face behind the inguinal notch, the free border more posteriorly, and 
the form and proportions of the various scutes, the lobe presents nothing to distinguish it 
especially from the White River species. 
Another specimen belonging to the Cope collection, | 359, presents some differences 
from the shell just described. The length is 255 mm., the or. 177mm. The front border 
is slightly concave in outline. The neurals are nearly as wide as those of the larger specimen 
just described. The first suprapygal is pentagonal, not bifurcated. The second is 23 mm. 
high and 56 mm. wide, and appears to include within itself the limbs of the usually bifurcate 
first suprapygal. There is a rather sharp carina along the sides above the bridge. The 
anterior vertebral scute is hardly as wide as are the second and the third; while the fifth is but 
little wider than those just mentioned. 
T C 
