174 



bono I would suspect that it belonged to Chisternon, rather than to either 

 Emys Carteri or Baptemys wyomingensu. 



HYBEMYS. 



Hybemys arenarius. 



Two little specimens, obtained by Professor Hayden, in the Tertiary for- 

 mation of Little Sandy Creek, Wyoming, appear to indicate a previously 

 undescribed turtle, to which the above name was given. They consist of 

 a detached marginal bone, and a fragment of a costal plate of a species 

 about the size of the common spotted turtle, E?nys guttata. The bones are 

 unusually thick in proportion to their breadth, compared with those of ordi- 

 nary recent Emydes. Their surface is smooth and strongly marked by the 

 lines of separation of the scute areas. The costal ridge on the interior of the 

 costal plate is scarcely perceptible ; the costal capitulum is rather stouter 

 than in Emydes. 



The marginal plate represented in Fig. 9, Plate XV, is especially remark- 

 able, and it is upon its peculiarity that the genus is inferred. It would appear 

 to correspond with the ninth of the series, and has the same form as in the 

 corresponding plate of ordinary Emydes. The outer portion of the upper 

 surface, strongly defined by the groove of the costal scute, exhibits at its fore 

 and back part a half-circular boss, occupying the middle of the marginal 

 scute areas. As we may safely infer the other marginals to have the same 

 construction, it follows that the margin of the carapace is ornamented with a 

 circle of hemispherical bosses, each of which is crossed by the sutures of the 

 marginal bones. 



ANOSTEIRA. 



Anosteira ornata. 



Among the many remains of turtles from the Bridger Tertiary formation, 

 submitted to my examination from time to time, by Dr. Carter and Professor 

 Hayden, there were a few isolated plates of peculiar character which were 

 described and referred to a genus and species under the above name. Sub- 

 sequently Dr. Carter discovered many parts of a shell of the same species, 

 which we have endeavored to collocate as represented in Figs. 1, 2, Plate 

 XVI. 



Anosteira is a remarkable genus, very unlike any other turtle, previously 



