596 



OBSERVATIONS ON THE RODENTIA. 

 71 



Skull and lower jaw of Oeomys umbrinus ? 



The same skull (Geomys) possesses two or three other pe- 

 culiar characters which are worthy of notice, particularly 

 the broadly expanded and almost flat form of the glenoid 

 cavity of the temporal bone, the very small size of the ant- 

 orbital foramina, which consist merely of two short vertical 

 slits, and the straightness of the nasal bones ; these are but 

 very slightly broader at the apex than at the base, and not 

 distinctly expanded in front as in other Arvicolce. The in- 

 terparietal bone is small and nearly of a semicircular form. 



72 



Skull and lower jaw of Spalax typhlus. 



The skull of Spalax typhlus (fig. 72), like that of Geomys, 

 has a broad and very slightly concave glenoid cavity to the 



