RODENTIA. 589 



inhabitants of hot climates, with the exception of the common 

 Porcupine {H. cristata), which occurs in southern Europe and 

 in the north of Africa. In the genus Atherura of Asia and the 

 Indian Archipelago, the tail is terminated by a bundle of flat- 

 tened homy strips. In the genus Erethizon, represented by the 

 Canada Porcupine [E. dorsatum) of North America, the quills 

 are short, and are half hidden in the hair. 



The nearly-allied genus Cercolabes is South American, and it 

 is distingiushed from the preceding by the possession of along 

 prehensile tail. In fact, Cercolabes, like so many of the in- 

 habitants of this wonderful continent, is adapted for an arbo- 

 real life, instead of being confined to the ground. 



Fam. 4. CastoridcR. — The best-known example of this family 

 is the Beaver {Castor fiber). The distinctive peculiarities of 

 the family are the possession of distinct clavicles, the posses- 

 sion of five toes to each foot, and the fact that the hinder feet 

 are mostly webbed, adapting the animal to a semi-aquatic life. 



The Beaver is a large Rodent, attaining a length of from 

 two and a half to three feet. Naturally it is a social animal, 

 living in societies, and this is still the case in America ; but in 

 northern Europe and Asia, where the animal has been much 

 hunted, it leads a solitary life. When living in social commu- 

 nities the beavers build dams across the rivers, as well as habi- 

 tations for themselves, by gnawing across the branches of trees 

 or shrubs, and weaving them together, the whole being, after- 

 wards plastered with mud. In this last operation the tail, which 

 is flattened and scaly, is employed very much as a mason uses 

 his trowel. There is no doubt but that the Beaver shows ex- 

 traordinary ingenuity in these and similar operations ; but there 

 can be equally little doubt as to the greatly-exaggerated stories 

 which have been set afloat in this connection. The Beaver is 

 hunted chiefly for the sake of the skin, but also for the sub- 

 stance known as castoreum. This is a fatty substance, secreted 

 by peculiar glands, and employed as a therapeutic'agent. 



There are two other members of the Castoridce which are 

 likewise largely captured for the sake of their skins. One of 

 these is the Musquash (Fiber Zibethicus), which inhabits North 

 America, and the other is the Coypu {Myopotamus coypus), 

 which inhabits burrows in the banks of rivers in Chili. In the 

 Musquash the hind feet are not completely webbed, and the 

 tail is moderate in size, "and covered with short hairs and small 

 rounded scales. In the Coypu the hind feet are webbed, but 

 the tail is long, rounded, and furnished with scales and scat- 

 tered hairs. 



Fam. 5. Muridiz.— The fifth family of Rodents is that of 



