904 RODENTIA 



side the median tubercle is much smaller than either of the two 

 between which it lies. 



Remarks. — The common squirrel in any of its geographical or 

 seasonal phases is so readily distinguishable among the mammals 

 of Europe as to require no special comparisons with other 

 members of the fauna. 



KEY TO THE EUROPEAN FORMS OP SGIURVS VULGARIS. 



White of underparts restricted to median region ; 



hind foot about 50 mm. (Southern Spain) S. ..<. bietkvs, p. 923. 



White of underparts not restricted to median region ; 

 hind foot 55 to 70 mm. 

 Tail drab, fading in spring and summer to pale 

 buff, never strongly reddish or blackish (British 



Islands) S. v. lencoums, p. 907. 



Tail varying from red to black, never drab or bufiy. 

 Condylobasal length of skull usually about 49 to 

 55 mm. ; mandible 34 to 37-6 mm. (Spain). 

 Tail without white on under surface; skull 



49 to 51 mm. (North-central Spain) S. v. iiun«inti<ts, p. 914. 



Tail usually with conspicuous whitish median 

 area on under side (this sometimes repre- 

 sented by a few white hairs only). 



Muzzle and cheeks rusty (Central Spain) ,S. *;. infwmtus, p. 916. 



Muzzle and cheeks whitish ot pale grey 



(South-western Spain) S. v. segurse, p. 917. 



Condylobasal length of skull usually about 44 to 

 49 mm. ; mandible 31 to 34 mm. 

 Dark brown phase essentially absent (North- 

 ern). 

 Winter pelage smoke-grey, the back strongly 

 tinged with red (Scandinavian Penin- 

 sula, except extreme north) S. v. vulgaris, p. 905. 



Winter pelage pearl-grey, the back scarcely 

 or not tinged with red (Extreme north 

 of Scandinavian Peninsula, east into 



Eussia) S. v. vrtrius, p. 906. 



Dark brown phase not infrequent, sometimes 

 dominant (Central and southern). 

 Upper parts in dark brown phase much 

 darker anteriorly than posteriorly 



(Greece) S. v. lilxus,-^. 913. 



Upper parts in dark phase not noticeably 

 darker anteriorly than posteriorly. 

 Rostral portion of skull unusually short 



and broad (Pyrenees) S. v. alpinw, p. 914. 



Rostral portion of skull normal. 



Winter pelage of red phase essentially 

 without suffusion of grey on sides 



(Italy) & v. italiaa, p. 912. 



Winter pelage of red phase strongly 

 suffused with grey on sides. 

 Red in both winter and summer, 

 clear bright rufous (East-central 



Europe) S. v.fuscoater. p. 910. 



Red in Doth winter and summer, 

 rufous strongly tinged with chest- 

 nut (West-central Europe) ti. v. rtissus, p. 909. 



