358 GEOGEAPHICAL AND GEOLOGICAL DISTRIBUTION, 



has already been adverted to in the general treatment of the North 

 American fauna. The jerboas or true jumping-mice are distributed 

 from the eastern confines of the Mediterranean to India, and south- 

 ward over nearly the whole of Africa. Alactaga jaculus extends 

 its range westward from the Altai Mountains to the Danube, and 

 Dipus sagitta from the far east of Mongolia to the Volga. The 

 largest representative of the family is the Cape jumping-hare (Pede- 

 tes Gaffer), whose range extends from Mozambique and Angola to 

 the southern extremity of the African continent. Only one trans- 

 Atlantic species is known, the American jumping-mouse (Zapus 

 Hudsonius), which is distributed over almost the whole of the 

 North American continent between Labrador and Mexico. 



Of the squirrel forms, or sciuromorphs, the family of squirrels 

 (Sciuridae), which comprises, in addition to the ordinary and flying- 

 squirrels, also the marmots and prairie-dogs, embraces very nearly 

 all the species belonging to the group. The true squirrels (Sciurus), 

 of which there are probably not less than one hundred species, are 

 extensively distributed over all of the continental divisions of the 

 globe with the exception of the Australian, being limited only or 

 primarily by a deficiency in the forest growth. The headquarters 

 of the genus might be said to be the Oriental region, which holds 

 nearly one-half of all the recognised species ; no species are known 

 from either Madagascar or the West Indian islands, although sev- 

 eral forms inhabit the larger islands of the Malay Archipelago 

 Java, Borneo, Sumatra, and Celebes. 



In the whole of Europe, excluding the Caucasus, there is but a 

 single species of squirrel, Sciurus vulgaris, whose range extends 

 from the extreme north to the Mediterranean, and eastward through- 

 out Siberia. In the Engadine it ascends the Alps to an elevation of 

 7,000 feet. North America north of the Mexican boundary possesses 

 six species (and about an equal number of well-marked varieties de- 

 pending upon size and colouration), of which the most familiar form 

 is the common chickaree (Sciurus Hudsonius), in its several varieties 

 eastern chickaree, western chickaree, Fremont's chickaree, and 

 Richardson's chickaree whose range extends from the northern 

 limit of forest vegetation to the highlands of Georgia and Alabama ; 

 on the Atlantic border its southern limit appears to be Delaware Bay. 

 This is the only species of squirrel found north of the Canadian 

 boundary. The flying-squirrels are usually separated into two dis- 



