TESTUDINID^. 



389 



In general the structure of the skull resembles that of the genus Gopherus, and therefore 

 in general that of Testudo. As regards its size, in case the ratio of the portion behind the 

 orbits to that from the postfrontal bones to the tip of the snout was the same as in the skull of 

 either Gopherus polyphemus or of Testudo tabulata, the whole length from snout to occipital 

 condyle must have been about 75 mm., and the breadth at the quadrates about 61 mm. The 

 orbits are large, about 20 mrn., hardly smaller proportionately than they are in the Testudo 

 mentioned. The interorbital space is 15 mm. wide. The upper surface of the skull, from the 

 nostrils to near the hinder border of the frontals, is gently convex. The parietals are more 

 convex both longitudinally and transversely. 



The sides of the face just behind the nostrils were nearly perpendicular. The nasal 

 opening is nearly quadrate, and was 16 mm. wide and about 10 mm. high. The cutting- 

 edges of the maxillaries make about the same angle with each other that they do in T. tabulate! 

 and G. polyphemus. There is a broad notch in the cutting-edge at the premaxillary symphysis; 

 and behind this on each side there is an indication of a tooth. The masticatory surfaces of 

 the upper jaws resemble in breadth those of the genus Gopherus. Along the middle of each 



492 



FIGS. 488-492. Stylemys nebrascensis. 



490. 

 Skull and humerus. 



488. Upper view of skull. Xi. No. 1571 Carnegie Museum. 



489. Lower view of same. Xi. 



490. Side view of same. Xi. 



491. Right humerus, dorsal view. X. No. 700 A.M. N. H. 

 491. Right humerus, proiimal end. X. 



surface there is a tootht ridge which runs parallel with the cutting-edge. In front, a longi- 

 tudinal ridge runs backward from the symphysis, as in G. polyphemus, a character which has 

 led to the separation of the North American species of Testudo, to form the genus Gopherus. 

 In Stylemys a less elevated ridge is developt on the inner border of the maxillary. The structure 

 of the upper jaw is like that of Gopherus polyphemus, except that in Stylemys the masticatory 

 ridges do not join the longitudinal ridge. 



As in Testudo and Gopherus, the palate is archt upward high above the level of the 

 masticatory surfaces; and there is a sharp ridge which, starting on the vomer, is continued 

 backward to the hinder end of the latter bone and on the conjoined edges of the pterygoids. 

 The width of the vomer, where it articulates with the premaxillanes and the maxillaries, is 

 considerable, as it is also in G. polyphemus. In T. tabulata the vomer is narrow anteriorly and 

 articulates only slightly with the maxillaries. 



The vaulted roof of the mouth continues backward as far as the bones of the skull are 

 preserved, and judging from Testudo, to a line joining the front borders of the articular ends 

 of the quadrates. In the specimen the vaulted roof has been forced upward and broken across 

 the middle, and a portion of it is missing; but the hinder end of the vomer is present, and 

 extended backward about 25 mm. from the anterior end. The palatines extend backward 

 as far as the hinder end of the vomer. The nasopalatme and posterior palatine foramina have 

 the same positions as in Gopherus. The former is rather small. 



The postfrontal and jugal bones are missing; as are also the prootics, squamosals, and 

 quadrates. 



