GEOLOGICAL 8UK\'Ey OF THE TERRITORIES. 623 



middle portion slightly convex forward. The suture separating the 

 femoral and anal scuta is similar, but reversed in direction, presenting 

 two obtuse right angles, two portions being transverse and one longi- 

 tudinal on each side. 



From Black's Fork and other localities. 



Baena arenosa, Leidy. 



Loc. cit. Baena affink, Leidy, ibid. 



A perfect specimen of smaller size than those of the preceding species, 

 and one about equal to the Piyehemys rvgosa, is not dissimihir in form. 



The carapace is strongly convex, and all its component parts, as well 

 as those of the plastron, are co-ossified. The sutures of the intersternal 

 bones are visible. The posterior end of the carapace is arched upward, 

 and smoothly excavated; the . postero-lateral borders are thin, and 

 deeply notched as the ends of the scutal sutures. Similar but shal- 

 lower emargiuations mark the borders of the marginal scuta. The 

 anterior margin is slightly concave. The lobes of the plastron are 

 narrow, the posterior wider and slightly emarginate. The bridge is 

 wide, and not more than half as long as the width of the base of the 

 posterior lobe. 



The general surface is minutely rugose or shagreened, on the plastron 

 strongly so, and without other sculpture. The carapace is marked by 

 strong grooves disposed in a regular manner. A double groove extends 

 along the median line of the second, third, and fourth vertebral scuta. 

 Other grooves are nearly parallel to this one, whose extremities di- 

 verge to the angles of the vertebral scuta. At the anterior angles of 

 the costal scuia oblique grooves converge toward the vertebrals, and 

 are continued backward as parallel to the median line. They are sepa- 

 rated by parallel tuberosities. On the first and last vertebral scuta 

 there are transverse grooves next the adjacent vertebrals, and longi- 

 tudinal ones toward the margins of the carapace. 



The scuta are well marked. The marginals are all longer than wide, 

 except the four preceding the last, which are all wider than long. The 

 last is snboval, and is very small, while the anal is altogether wanting. 

 The nuchal is divided, (it is single in B. hehraica;) the first marginal is 

 very small and projecting; the third is longer, while the fourth, fifth, 

 and sixth are rather short. The vertebral scuta are all longer than 

 wide, and the fourth is deeply emarginate to receive the last scute. 

 The first is a broad triangle with anterior angle truncate, and the two 

 basal ones cut off to a less degree. 



The scutal sutures of the plastron are but little sinuous. The intergu- 

 lars have precisely the form of gulars of Emydes. The posterior guhir 

 suture crosses the median line a short distance posterior to those of 

 theintergulars, and each half consists of an obtuse V directed backward. 

 The posterior humeral suture originates in front of the axilla. There 

 are four intermarginal scuta on the one side and three on the other, 

 the additional one being a small one behind the left axillary. The 

 femoro-anal suture is nearly straight. 



Measurements. 



M. 



Length of carapace, (axial) 0. 4oO 



Width of cara]);ice, (axial) '240 



Length of plnstrou 290 



Length of anterioi- lobe 0S2 



Length of posterior 08,") 



Width of extremity anterior lobe 038 



