BAENID&. 71 
On the left" bridge there are four inframarginal scutes. Of these the second is the smallest, 
the first and the fourth the largest. All the ‘plastral, as well as the carapacial scutes, agree 
closely with those of Leidy’s type. 
A portion of the pelvis is preserved (fig. 51). So far as can be determined, it agrees well 
with that of the type of the species. Unfortunately, the upper end of the ilium is missing. 
Professor Cope figured and described what he regarded as a specimen of B. arenosa (Vert. 
Tert. Form. West, p. 148, plate xvi, figs. 1,2). The specimen is in the American Museum and 
has the number 1112. The present writer regards it as belonging to B. riparia. 
Professor Cope has described and figured also a portion of a carapace found by him in the 
Wasatch beds of New Mexico. As the type of B. arenosa 
was discovered in the lowermost beds of the Bridger, it is 
not impossible that the species may occur in the Wasatch; 
but the identification based on a part of the shell is not 
to be depended upon. 
However, the American Museum expedition of 1906 
into the Wasatch deposits of Wyoming secured a specimen 
of Baéna which is referred to this species. This was found 
near Knight’s Station, not far from Evanston. The level 
was about 200 feet above Bear River. The catalog number 
of the specimen is 6041. About one-third of the carapace 
in front has been eroded away, but otherwise the shell is 
in fair condition. The length of the carapace was origi- 
nally about 240 mm. The width at the middle of the length 
is 222 mm., and this width is fully maintained to opposite the ends of the femoro-anal sale. 
So far as can be determined this specimen differs from most Bridger specimens in the greater 
smoothness of the areas of the vertebral scutes; but this appears to have been nearly the 
condition of Leidy’s type. Cope’s specimen obtained in the Wasatch of New Mexico and 
referred by him to the present species had the back sculptured as in most Bridger specimens. 
It appears best, until more is known about the Wasatch form, to identify it as B. arenosa. 
2 
3° 
Fic. 51.—Baéna arenosa. X 
Pelvis seen from below. 
Baéna sima sp. nov. 
Plate 13, figs. 2, 3; plate 14, figs. 4-6; plate 15; text-figs. 52-56. 
The present species has for its type No. 5971 of the American Museum of Natural History. 
This specimen was collected by that museum’s expedition of 1903 into the Bridger beds. The 
locality is on Little Dry Creek, south of Fort Bridger, and the level is that designated as B. The 
specimen furnishes nearly the whole of the shell, the skull, with the lower jaw, a number of 
vertebra, and portions of the limb bones. 
The bones of the shell are so thoroly co-ossified that few of the sutures can be made 
out. The carapace (fig. 52) has an axial length of 360 mm.; the width was close to 260 mm. 
It was apparently rather elevated. There is no depression along the midline. In outline the 
—— —__ Carapace was pointed i in front and somewhat contracted behind. 
Wengen | “Width: Posteriorly there is in the border, over the tail, a rather deep 
Vertebral. 
igen excavation 72 mm. wide. The posterior peripherals are flared 
: ‘ ‘e upward. The surface of the carapace is very uneven, being 
3 81 6 everywhere covered with coarse pustular elevations; just outside 
4 79 82 of the third and fourth vertebral scutes there are some longitu- 
5 4 8 dinal wrinklings. About 25 mm. outside of these vertebrals there 
SSS SS are seen on each side distinct traces of a lateral carina. The 
median symmetrically arranged folds and grooves seen in B. arenosa are here quite indistinct. 
The nuchal scute has a fore-and-aft width of 16 mm. and a transverse extent of about 40mm. 
The first vertebral is 51 mm. long and 80 mm. wide; but there appears to be on the left side 
a small supernumerary costal scute cut out of its normal area. The other scutes have the areas 
given in the table. 
Outside of the nuchal scute there is, on each side, a minute triangular marginal scute. 
The next one, the second, is 21 mm. long on the free border and 21 mm. high. The third is 
