20 



Annals of the Carnegie Museum. 



skull in the collection made by Dr. Baur for the University of Chicago ; 

 but with neither of these skulls was there any of the shell. The im- 

 portance of the presence of the shell will be realized when it is re- 

 membered that the species was based on the shell and that there are a 

 few species of the closely related genus Testudo in the same formation. 



Fig. 9. Superior view of skull of Stylemys nebrascensis Leidy. L 

 Fig. 10. Inferior view of skull Stylemys nebrascensis Leidy. \. 



From the parts of the shell and limb bones the writer has been con- 

 vinced that Stylemys belonged, without doubt, near Testudo and that 

 it was at the same time a distinct genus. What is now known about 

 the skull confirms these conclusions. 



The length of the skull discovered by Mr. Douglass is 38 mm.; the 



width at the quadrates, 30 mm. 

 The interorbital space is 10.5 mm. 

 wide. The antero-posterior diam- 

 eter of the orbit is 11 mm.; the 

 vertical, 9 mm. The pterygoid 

 region where narrowest is 10 mm. 

 wide. The palate is deeply exca- 

 vated and a low ridge runs along its 

 middle line. The lower jaw remains in its natural position and hides 

 the crushing surfaces of the upper jaw. The symphysis is short. 



As Seen from the figures (Figs. 9-11), this skull corresponds in all 

 essentials with that of Testudo. It is identical, too, with the skull 

 preserved at Princeton, which displays the crushing surfaces of the 

 upper jaws. These present the same arrangement that we find in the 

 living genus Gopherus {Xerobates, Agass.), there being especially a 

 longitudinal ridge at the symphysis of the premaxilloe. On examin- 

 ing closely the Pittsburgh specimen this ridge is seen to be present. 



Fig. 11. View of right side of sku 

 of Stylemys nebrascensis Leidy. A. 



