RODENTIA, CHEIROPTERA, AND INSECTIVORA. 407 



.1—1 0—0 2—2 3—3 



i ; c ; pm ; m =24. 



2 — 2 0—0 1 — 1 3 — 3 



Fam. 3. Cavidce. — In this family are the living Capybaras 

 {Hydrochoerus), Agoutis {Dasyprocta), Pacas {Coelogenys), &c., 

 characterised by their absence of clavicles, their rudimentary 

 tail, their unguiculate toes, and their general possession of 

 eight rootless molars in each jaw (fig. 683). Almost all 

 the existing members of this family belong to South America, 

 and this continent has been peopled during Post-Tertiary 

 times with numerous species more or less nearly allied to 

 living forms. Thus, the Brazilian bone-caves have yielded 

 to the researches of Lund remains of Guinea-pigs {Ancetna), 

 Agoutis, Pacas, and Capybaras, all of which appear to be- 

 long to extinct species. The Capybaras {Hydrochoerus) seem 

 to have extended their range to North America during the 

 Post-Pliocene period ; while Cavies occur in South America 

 as early as the Pliocene. Eemains from the Miocene of 

 Europe have also been discovered indicating the past exist- 

 ence of Cavies and Agoutis in this region. 



Fam. 4. Hystricidce. — In this family are the well-known 

 Porcupines, distinguished from the other Eodents by the fact 

 that the body is covered with long spines or " quills," mixed 

 with bristly hairs. They have four molars on each side of 

 each jaw, and they possess imperfect clavicles. 



The genus Hystrix appears first in the Upper Miocene of 

 Europe, in the person of a species nearly allied to the living 

 H. cristata, and other forms appear in the Pliocene of the 

 same region. The H. venustus of the Pliocene of North 

 America is also related to the H. cristata of Southern 

 Europe. 



Fam. 5. Cercolabidce. — This family is hardly separable 

 from the preceding, the chief difference being that the 

 animals composing it spend more or less of their lives in 

 trees, and are therefore adapted for climbing. The only 

 fossil form referable to this family is a large Cercolahes found 

 in the Post-Pliocene cave-deposits of South America, in which 

 region the genus still survives. 



Fam. 6. Octodontidoi. — This family includes a large number 



