G20 GEOLOGICAL SURVEY OF THE TERRITORIES. 



M. 



No. 2. Width first costal, proximally 026 



Width lirst costal Ix'hiud rib, distally 014 



No. 3. Width middle costal 0:^1 



Two of the specimens from Cottonwood Creek. 



Plastombnus molopinus, Cope. 



Proceed. Amer. Philos. Soc, 1872, p. 461, (July 29,) Anostira. 



L First costal bone with wide rib, tlie aliform border behind it not more 

 than half its width. Suture for first costal distal, obliquely truncating 

 end of rib, vertical and not oblique. External surface of the same 

 coarsely pitted, and with (tbscnre oblique ribs. Median costals with 

 ai)proximated thick cix)ss-ribs, with obsolete punctatious between. 



This species is near the P. oedemius, but differs considerably in the 

 form of the first costal bone. The type is smaller than those of the 

 latter. . 



Measurements. 



M. 



Width first costal at extremity 0120 



Width lirst costal, .75 iuch from end 0210 



Width of a middle costal 0140 



Thickness of a middle costal 0055 



From the Bridger group, Wyoming. 



ANOSTIRA, Leidy. 



Proceedings Academy Nat. Sci., 1871, p. 10^ 



In this genus the epidermis was thin and adherent to the bones, and 

 not divided into scuta. The carapace is composed as in Emyd'uUc of 

 costal vertebral and marginal bones, the last united to the first by suture 

 and gomphosis. The series of vertebrals does not continue to the cau- 

 dal, except by the intervention of a pygal. The sternum is cruciform, 

 with narrow, longitudinal prolongations, or lobes, and narrow bridges. 

 It appears not to have possessed any fontanelles, but the presence of 

 mesosternum is not yet fully made out. The cranium and limbs are 

 unknown. This genus must be regarded as an interesting intermediate 

 type, 'connecting Plastomemis and CJieJydra, or Dcrmatemys. Tn skin 

 and sculpture it is identical with the first; in carapace and plastron, 

 most like Chelydra. 



Two species, a large and a small, are known. 



Anostira radultna. Cope. 



Proceed. Amer. Philos. Society, 1872, p. 555, (pnhlished October 12.) 



Based on two marginal bones, one from the front, the other from the 

 rear, of the carapace of an animal of twice the bulk of the largest Anos- 

 tire yet found. Apart from size, the sculpture is peculiar. It consists 

 in the anterior of closely packed vermi<;ular ridges which run out flat 

 on the posterior and upper edge. In the posterior it consists of>only 

 closely placed minute tubercles over the whole surface. 



Measurements. 



M. 



Length front on free edge • 0. 025 



Width front on free edge f'-^ 



Length posterior on free edge (*25 



Width posterior on free edge 025 



■ Bad Lands of Ham's Fojk, Wyoming. 



