126 



CHARACTERS OF VERTEBRATE ANIMALS 



which, as the name indicates, live upon the ground, are common 

 in the colder parts of the northern hemisphere. Much resembling 

 ordinary squirrels in appearance, they differ in the smaller size of 

 the tail, the absence of tufts to the ears, and the possession of large 

 cheek -pouches. They excavate burrows in the ground. The 

 Common Chipmunk {Tamias striata) of North America is a 

 good example. Flying-Squirrels possess a parachute-like fold of 

 skin on either side, much as in the Flying- Lemur (cp. p. 86). 

 They mostly range from India to Japan, but are also represented 

 in North America, Siberia, and East Europe. The Brown Flying- 

 Squirrel {Pteromys petaurista) is 

 the largest species. The African 

 Flying - Squirrels {Anomalurus), 

 mostly natives of West Africa, 

 differ from the preceding chiefly in 

 the structure of the tail and flying- 

 membrane. 



Least squirrel-like of the squir- 

 rel sub-group are the Susliks or 

 Gophers, found in much the same 

 regions as the ground-squirrels. 

 They are burrowing forms with 

 large cheek-pouches. The Com- 

 mon Suslik {Spermophilus citillus), 

 which ranges from Central Europe 

 to Siberia, has a short tail and very 

 small ears (fig. 86). The Striped 

 Gopher (5". tridecemlineatus) of North America is somewhat 

 better off as regards ears and tail, and is prettily marked with 

 stripes and rows of dots. 



Marmots are more stoutly built than squirrels, their ears being 

 smaller and their tails shorter, while cheek-pouches are present. 

 They are burrowing social forms, and their area of distribution 

 includes the colder parts of the northern hemisphere. A familiar 

 European type is the Alpine Marmot {Arctomys marmotta) of the 

 Pyrenees, Alps, and Carpathians. A common North American 

 form is the Woodchuck [Arctomys monax). 



The Prairie Marmots of North America are closely related to 

 the preceding. The best-known species is the Common Prairie 

 Marmot, often called "prairie-dog " {Cynomys ludovicianus), large 



Fig. 86. — The Common Suslik {Spermophillts 

 citillus) 



