92G 



RODENTIA 



and its genei'al form differs notably in the ciineate outline due 

 to the narrowness of anterior zygomatic region, the almost 

 uniformly convex dorsal profile, and the slight deflection of basi- 

 cranial axis, so that upper third or fourth of foramen magnum 

 is above level of alveolar line. Dorsal profile convex from front 

 of nasals to lambdoid ridge, sometimes with a slight flattening 

 in interorbital region and a faint posterior concavity ; ventral 

 profile similar, though less strongly convex ; posterior truncation 

 of brain-case nearly vertical, but occipital condyles projecting 



Fig. 188. 

 Citellus citellus. Nat. size. 



sufficiently to be just visible from above. Brain-case very 

 broadly ovate when viewed from above, its greatest Avidth 

 equal to length, its posterior width obviously exceeding than 

 that at postorbital constriction ; surface less rounded than in 

 Sciurus vulgaris, and lyrate figure formed by parietal ridges 

 much narrower ; lambdoid crest essentially as in S. vid(jaris, but 

 constriction just in front of occipital region less evident. Occiput 

 low, its general form as in Sciurus vulgaris, but contrast between 

 its height and that of middle of brain-case not especially marked ; 

 protuberances on posterior surface of occiput less noticeable than 



