74 FOSSIL TURTLES OF NORTH AMERICA. 
the midline. The height, after some crushing, is still 132 mm. The scallops of the hinder 
border are shallow. The surface of the carapace is sculptured as in the type. The symmetrical 
ridges and grooves found in B. arenosa and B. riparia are here obscure. On the hinder half of 
the carapace there are a few irregular longitudinal folds and a system of anastomosing 
ridges and pustular elevations. The outer ends of the costal scute areas, the marginal areas, 
and the whole anterior half of the carapace are much smoother. The nuchal scute is not 
divided. On each of the bridges there were four inframarginal scutes. The bridge region of 
fig. 53 has been completed from this specimen. 
No. 5907 of the American Museum was collected in 1903 by the writer at Grizzly Buttes, 
Wyoming. It may be regarded as a second paratype. It furnishes the shell, fragments of the 
skull, fhe pelvis, and some limb bones. The shell appears not to have been distorted by 
pressure. The plastron has exactly the length of that of the type. The width of the carapace 
is 290 mm.; the height above the bottom of the plastron, 150mm. On the right bridge there 
are only 3 inframarginal scutes, and the pectoral scute joins the sixth marginal. On the carapace 
the nuchal scute is not divided longitudinally. On each side, as in the: other specimens, is a 
small marginal followed by a much ‘larger one, that on the right side being larger. The super- 
numerary costals are not found at the sides of the first vertebral. 
The pelvis is represented by fig. 54. The shaft of the ilium, where narrowest, has a diam- 
eter of 10 mm. The expanded head is 34 mm. high and 33 mm. wide, while in Chisternon 
undatum the head is considerably higher than wide. The pubis is thin, 4.5 mm., slightly 
convex aboye, concave below. ‘The pelvis resembles closely that of the type of B. arenosa. 
Fig. 55 is that of the distal end of the humerus, seen from above. The radius is a terete 
bone 57 mm. long. Fig. 56 represents one of the digits. The right femur is 78 mm. long and is a 
stout bone with a minimum diameter of 8 mm. The plane passing thru the strongly comprest 
head falls outside the tibial border of the distal end far less than in a specimen of Trachemys 
elegans. ‘The tibia had a length somewhat exceeding 63 mm., and the least diameter of the 
shaftis7mm. The distal end of the fibula has a width of 13 mm. 
The greater portion of the lower jaw is present and it is of the same heavy construction as 
that of the type. Fragments of the roof of the skull show that the bones in the midline, behind 
the orbits, were 7 mm. thick. 
Baéna clara sp. nov. 
Plate 16, figs. 1, 2; text-figs. 57, 58. 
This species is based on a nearly complete shell which was collected by the American 
Museum expedition of 1893. It was obtained in the Bridger beds of Wyoming and bears the 
number 1675. The exact level and locality are not known. Only unimportant portions of the 
front of the carapace are wanting. 
The extreme length of the carapace (plate 16, fig. 1) is 362 mm.,; its width across the middle, 
where it is widest, is 300 mm. The shell is but little distorted by pressure. It is elegantly oval 
in form, with the edges of the hinder border of the carapace furnisht with shallow scallops, 
and with a deep excavation in the rear, as if for a large tail. The shell is flat transversely in the 
region occupied by the vertebral scutes. There is no carina, except along the fifth vertebral 
scute. Immediately i in front of this, for a short distance, there is a narrow median ridge, like 
that seen in B. arenosa. Over and behind the posterior legs the shell is flared Guevard and 
slightly upward. In front and behind the bone is rather thin; but anteriorly it soon thickens, 
so that over the fore legs it has a thickness of about 15 mm. At the sides the margins of the 
shell are massive. 
The carapace is smooth, with only some faint indications of the sculpturing seen in B. 
arenosa. 
The plastron (plate 16, fig. 2; text-fig. 58) has a length of 333 mm. in the midline. It was 
flat as far out as the bridges. From the inner ends of these the plastron rises upward and 
outward to the margins of the carapace, so that the latter stands some 50 mm. above the level 
of the plastron. ‘The highest part of the shell stood above the plastron about 150 mm. 
The anterior lobe of the plastron is tongue-shaped, rounded in front, and feebly notcht. 
In the figures it appears foreshortened, having been prest upward during fossilization. Its 
