74 FOSSIL TURTLES OF NORTH AMERICA. 



the midline. The height, after some crushing, is still 152 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 ot anastomosing 

 ridges and pustular elevations. The outer ends ot 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, the pelvis, and some limb bones. The shell appears not to have been distorted by 

 pressure. The plastron has exactly the length ot that of the type. The width of the carapace 

 is 290 mm.; the height above the bottom of the plastron, 150 mm. 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 above, 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 ot the 

 shaft is 7 mm. 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. 



Baena 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 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 outward 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 ^^ mm. in the midline. It was 

 flat as tar 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 ot the plastron is tongue-shaped, rounded in front, and feebly notcht. 

 In the figures it appears foreshortened, having been prest upward during fossilization. Its 



