THALASSEMYDID&. 15 3 
The pygal bone (figs. 189, 190) had a width of about 80 mm. along the free border. Some 
of the upper border has crumbled away, but the height of the bone was close to 65 mm. Its 
thickness a short distance below the upper border is 1g mm. The upper surface is concave fore 
and aft; convex from side to side. On the lower side the directions of these forms of surface 
are reverst. The free border is acute. The upper border was probably suturally articulated 
with the suprapygal. On neither the upper nor the lower side of this bone is there any trace 
of a sulcus. ; 
Of the eleventh peripheral Cope had no more than is now present, the hinder half, articu- 
lated with the pygal. It is concave from the free edge to the upper border on the upper surface, 
rather strongly convex on the lower surface. In the upper border there remains a portion of 
the deep pit for the rib-head of the eighth costal. The greatest thickness of the bone is 19mm. 
While a considerable part of the free border is broken away, that remaining seems to indicate 
that this border was emarginate, as was stated by Cope. No sulcus appears on this bone. 
Two of the costals represented are evidently those of the same pair. Cope thought they 
were those of the second pair. The proximal end was 82 mm. wide. One of the sutural 
borders is 11 mm. thick, and the suture is oblique to the surfaces of the bone. It was evidently 
overlapt by the bone to which it was articulated. The opposite border is only 5 mm. thick. 
Under C. repanda reasons have been given for regarding the border bearing the oblique suture 
as the anterior one; and the costals of the two species are so similar that the same rule applies 
here. As in C. repanda, the rib-head is strongly developt, as well as the rib in its course along 
Fics. 189 AND 190.—Catapleura ponderosa. Portions of type. 3. 
189. Pygal and eleventh peripheral. 190. Section along midline of pygal. 
the under side of the costal. As in C. repanda, this rib gets nearer and nearer the thickened 
side of the costal on its way toward the distal end. There is also a rough groove near the prox- 
imal end of the front of the ridge; but it is not so conspicuous as in the other species. More- 
over, it is seen only on the two costals supposed to belong to the second pair. 
On none of the costals or peripherals are there observed any remains of sulci, to mark the 
limits of the horny scutes. The costals are markt by very distinct branching vascular grooves. 
There is present a fragment of a plastral bone, which was interpreted by Cope as the 
hinder part of the left hypoplastron.- The writer finds it impossible to identify the bone satis- 
factorily. One border is obtuse and 14 mm. thick. The opposite border is thin and irregular. 
Only the proximal half of the right humerus is present. The long axis of the head 
measures 35 mm., the shorter 24 mm. The radial process is missing, but it continued to the 
head of the bone. The ulnar process lacks much of rising to the level of the head, and the ridge 
descending from it runs well down on the shaft. The planes of the radial and ulnar processes 
make with each other an angle of more than go°. The shaft of the bone is comprest, having 
a diameter of 15 mm. in the perpendicular plane; of 11 mm. in the horizontal. It is therefore 
comprest in a manner directly opposite to that of the Chelonide. 
The femur is that of the right side and lacks the distal end. The portion remaining is 93 
mm. long; and the whole bone must have been about 120 mm. long. As in the more primitive 
turtles, the head and the processes resemble those of the humerus. The head has diameters 
respectively of 23 mm. and 30 mm. 
