RODENTIA. 59 1 



tances. They are all of small size, and inhabit Russia, North 

 Africa, and North America. The Isest-known members of this 

 family are the common Jerboa {Dip^us ySgypticus), which lives 

 in societies and constructs burrows; the Jumping Hare (Pedetes 

 Capmsis) of South Africa, and the Jumping Mouse (Meriona 

 Hudsonicus) of North America. Here also may be placed the 

 Gerbilles (Gerbillus) of the Old World. 



Fam. 7. MyoxidcB. — The members of this family are com- 

 monly known as Dormice, and they are often included in the 

 following family of the Squirrels and Marmots. They only re- 

 quire to be mentioned, as they must not be confounded with 

 the tru6 Mice {Muridce) on the one hand, or the Shrew-mice 

 (Soricidce) on the other j the latter, indeed, belonging to an- 

 other order {Insedivora). The common Dormouse \Myoxiis 

 avellanarius) is a British species, and must be familiarly kno\\ n 

 to almost everybody. No species of this family have yet been 

 described from the New Wqrld. 



Fam. 8. Sciuridm. — This is the last family of Rodents which 

 calls for any special mention, and it comprises the true Squin-ejp, 

 the Flying Squirrels, and the Marmots. • 



The true Squirrels (Sciurus) are familiarly known in the 

 person of the common British species (Sciurus vulgaris), and 

 the equally common Gray Squirrel {S. cinereus) of the 

 United States. Numerous species more or less closely allied 

 to these occur in other countries, and they are especially 

 abundant in North America. 



In the genera Pteromys and Sciuropterus, or Flying Squirrels, 

 there is a peculiar modification by which the animal can take ex- 

 tended leaps from. tree to tree. The skin, namely, extends in 

 the form of a broad membrane between the hind and fore legs, 

 and this acts as a kind of parachute, supporting the animal in 

 the air. There is, however, no power whatever of true flight, 

 and the structure is identically the same as what we have j/re- 

 viously seen in the Flying Phalangers {Fetaurus), which take 

 the place of the Flying Squirrels on the Australian continent. 

 The Flying Squirrels are found in southern Asia, Polynesia, the 

 north-east of Europe, Siberia, and North America. 



The Marmots {Arctomys), unlike the true Squirrels, are ter- 

 restrial in their habits, and live in burrows. Various inter- 

 mediate forms, however, are known, by Avhich a transition is 

 effected between the typical Squirrels and the Marmots. Such, 

 for example, are the Ground Squirrels {Tamias) of Europe, 

 Asia, and North America. There are numerous species of this 

 family inhabiting various parts of Europe and northern Asia, 

 and generally distributed over the whole of North America. 



