282 THE GEOGRAPHY OF MAMMALS 



Deductions 



1. The Order Rodentia is the most numerous of all the 

 chief Mammalian groups, containing nearly 1400 species, 

 which are divided into 170 genera and 21 families. 



2. The Rodents are distributed all over the world both 

 in temperate and tropical climes, and are abundant every- 

 where, both in species and individuals, except in Australia 

 where they are poorly represented. 



3. The most all-pervading and numerous family of the 

 Rodents is the Muridte (Mice), which are upwards of 600 

 in number and are the only members of the group met 

 with in Australia and Madagascar. In Madagascar the 

 Muridte are represented by a small group of indigenous 

 genera. 



4. The Porcupine-like Rodents, of which there are 

 seven families, are specially characteristic of the New 

 World, only the typical Porcupines (Hystricid&) and five 

 peculiar genera of Octodonts being inhabitants of the New 

 World. 



5. Two families of Rodents, the Pocket-gophers (Geo- 

 myidiB) and the Kangaroo-rats {Heteromyidie), are speci- 

 ally characteristic of the Nearctic Region, the Jerboas 

 {Dipodidze) of the Palsearctic, and the Sand-rats (Bathy- 

 ergidte) of the Ethiopian Region. 



