223 



hemispheres are nearly as much convoluted as in the latter, and measure 

 about 4£ inches in length and breadth. 



A third specimen, which may likewise be suspected as belonging to Had- 

 rohyus, is a large atlas, which measures 5 inches in width between the outer 

 acute borders of the articular cups for the occipital condyles, and about 4^ 

 inches from the neural tubercle to the hypapophysis. The vertebra differs in 

 several important points from the atlas of the rhinoceros, horse, ox, &c, but 

 the want of the requisite means of comparison prevents me from determin- 

 ing its nearer relationship. 

 » 



AN UNDETERMINED CARNIVORE. 



A supposed carnivorous animal of large size is indicated by the portion of 

 a large canine tooth, represented in Fig. 26, Plate VII. The specimen per- 

 tains to the Condon collection of Oregon fossils. 



CHELOMA. 



Testudinidce. 



STYLEMYS. 



The extinct genus of turtles above named, and originally described from 

 remains found in the Miocene Tertiary formation of the Mauvaises Terres of 

 White River, Dakota, was most nearly related with the existing land-tortoises. 

 The shell is of the simplest form, and is about as prominent as in the less 

 vaulted forms of the living species of Testudo, or the more vaulted ones of 

 the terrapenes. The proportions nearly accord with those of our southern 

 gopher, but the carapace is more uniformly convex. 



The carapace is most prominent just back of the middle, and is abruptly 

 rounded posteriorly as usual in the tortoises. The margin is entire, feebly 

 emarginate in front, somewhat expanded and everted over the axillary spaces, 

 and in a less degree everted over the inguinal spaces. 



The plastron holds the ordinary proportions to. the carapace as in Testudo 

 and Emys. It is for the most part flat, and only moderately turned up in 

 front. The extremities are nearly equal and rounded. The anterior is 

 slightly narrowed ; the posterior is moderately notched. 



The number, shape, and relations of the bones of the shell are nearly the 

 same as in Testudo and Emys. The number of the vertebral plates is ten, 

 occasionally eleven, from subdivision of the usual eighth plate. 



