CHAP. XVII.] 



MAMMALIA. 



237 



FAMILY 63. CHINCHILLID^E. (3 Genera, 6 Species.) 



The Chinchillidse, including the chinchillas and viscachas, are 

 confined to the alpine zones of the Andes, from the boundary of 

 Ecuador and Peru to the southern parts of Chili ; and over the 

 Pampas, to the Kio Negro on the south, and the Eiver Uruguay 

 on the east. Chinchilla (2 sp.), the true, chinchillas, are found 

 in the Andes of Chili and Peru, south of 9 S. lat., and from 

 8,000 to 12,000 feet elevation (Plate XVI. vol. ii. p. 40) ; Lagi- 

 dium (3 sp.), the alpine viscachas, inhabit the loftiest plateaus 

 and mountains from 11,000 to 16,000 feet, and extend furthest 

 north of any of the family ; while Lagostomus (1 sp.), the vis- 

 cacha of the Pampas, has the range above indicated. The family 

 is thus confined within the limits of a single sub-region. 



Extinct CJiinchillidce. Lagostomus has been found fossil in 

 the caves of Brazil, and in the Pliocene deposits of La 

 Plata. The only known extinct forms of this family are Ambly- 

 rhiza and Loxomylus, found in cavern-deposits in the island of 

 Anguilla, of Post-Pliocene age. These are very interesting, as 

 showing the greater range of this family so recently ; though its 

 absence from North America and Europe indicates that it is a 

 peculiar development of the Neotropical region. 



FAMILY 64 OCTODONTIDJE. (8 Genera, 19 Species.) 



GENERAL DISTRIBUTION. 



