SCTCROPTERUS 



943 



less of the surface of parietal is visible ; occiput very low, its 

 height above lower lip of foramen magnum about one-half 

 mastoid breadth, its dorsal and lateral margins forming a flattened 

 curve much less than a semicircle in extent ; foramen magnum 

 decidedly wider than high ; surface of occipital with very obscure 

 swellings between foramen magnum and lambdoid ridge ; par- 

 occipital processes very slender ; basioccipital rather narrow and 

 long, its width anteriorly about one-half median length, its 

 lateral ridges obsolete, not tending to form processes as in Sciurus 

 vulgaris and Citellus ; auditory bullae sub-circular in general 

 outline, their form essentially as in Sciurus vulgaris, but their 



FIG. 195. 

 Sduropterus russims. Nat. size. 



size actually as well as relatively greater, the antero-posterior 

 diameter equal to distance from front of bulla to front of w 1 , the 

 lateral diameter to outer margin of meatus fully \\ times least 

 width of basioccipital ; anterior upper margin of meatus developed 

 into a conspicuous forward-curved flange ; petrosal tending to be 

 exposed in region above meatus instead of on occipital surface. 

 Interorbital region decidedly longer than broad, its surface 

 noticeably concave laterally, so that bases of postorbital processes 

 are evidently above level of median region; notch at anterior 

 base of postorbital process large, always open; postorbital 

 processes long and slender, strongly curved downward, the orbit 



