94 COLIN CLOUT'S CALENDAR. 



mented by extensible folds of loose skin stretching 

 between the legs or the fingers. 



A group which shows so much variety of specialisa- 

 tion for its peculiar functions is likely to be an old one ; 

 and in fact the squirrels rank among our oldest surviv- 

 ing indigenous mammals. As a class, they date back as 

 far in geological time as the lower miocene ; and even 

 our English species must have inhabited this country, 

 practically unchanged in appearance or habits, for many 

 thousands of years, except when driven temporarily 

 southward by stress of passing glacial periods. 



