isa en in.*:. 



7 1 



On the left^bridge there are tour 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 ot 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. \\ est. p. 14S, plate xvii, figs. I, 2). The specimen is in the American Museum and 

 has the number 1 1 12. 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 

 ot Baena 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 

 ot the specimen is 6041. About one-third of the carapace 

 in front has been eroded away, but otherwise the shell is 

 in tair 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 sulci. 

 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. 



FlG. 51. Baena arenosa. X. 

 Pelvis seen from below. 



Baena sima sp. nov. 

 Plate 13, figs. 2, 3; plate 14, figs. 4-6; plate 1^; text-figs. ,-z-^. 



The present species has for its type No. 5971 of the American Museum of Natural Historv. 



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 



vertebrae, and portions ot 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 in front and somewhat contracted behind. 

 Posteriorly there is in the border, over the tail, a rather deep 

 excavation 72 mm. wide. The posterior peripherals are flared 

 upward. The surface of the carapace is very uneven, being 

 everywhere covered with coarse pustular elevations; just outside 

 ot the third and fourth vertebral scutes there are some longitu- 

 dinal wrinklings. About 25 mm. outside of these vertebrals there 

 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 transverseextentof 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 



