900 



RODENTIA 



laterally it barely extends on inner surface of thigh and forearm ; 

 line of demarcation well defined. Two colour phases occur, one 

 characterized by the predominance of red, the other by that of a 

 dark, sometimes almost blackish brown. The dark phase is often 

 incorrectly spoken of as melanistic. In a general way the phases 

 have a geographical significance, as the red is dominant at the 

 north, the dark brown at the south. The winter pelage is 

 everywhere lighter, brighter and more greyish than the summer 

 pelage. In regions where both colour pliases occur four normal 

 combinations of phase and pelage will be found in any consider- 

 able series of specimens. Apai't from these combinations and 

 their intermediate stages individual variation in colour is not 

 unusually great. 



Sktdl. — In general the skull is broad, smooth and rounded, 

 with large, deep brain-case and small rostrum, the basicranial 



Fig. 186. 

 Sciiirus vulgaris. Nat. size. 



axis bent downward so that foramen magnum is entirely below 

 level of alveolar line. Dorsal profile flat or faintly and irregularly 



