136 THE NEOG^EIC REALM. [CHAP. 



tropical and the Sonoran regions. Lastly, the Antillean sub- 

 region includes the West Indian Islands, exclusive of Trinidad, 

 which for zoological purposes may be regarded as part and parcel 

 of the South American continent. 



From the survey of the fossil forms it has been shown that 

 during the Plistocene epoch the mammalian fauna of the Chilian 

 and Brazilian sub-regions was similar, and it may consequently be 

 inferred that the present differentiation of the two areas in this 

 respect is a comparatively modern feature, probably due to 

 the disappearance of the forests from the Argentine. At the 

 present time the mammalian fauna of the Brazilian sub-region is 

 essentially that of the Neotropical region as a whole, nearly all the 

 characteristic groups being present within its limits, while several 

 are almost or quite peculiar to it. Among the latter, the great 

 ant-eater (Myrmecophaga) is practically confined to this sub-region \ 

 while most of the sloths and marmosets are limited to it, although 

 a few extend northwards into or through the isthmus. The pacas 

 (Ccelogenys), and the giant armadillo (Priodon} the sole repre- 

 sentative of its genus are likewise restricted to this tract ; as 

 is the bush-dog (Icticyon), and also one genus of tree-porcupines 

 ( Chcetomys], while most of the spiny rats (Echinomys and Loncheres) 

 are confined to it. The carpincho (Ifydroc/icerus) the largest 

 of living rodents likewise chiefly pertains to the Brazilian 

 region, although extending southwards into Uruguay. The 

 American monkeys are also very abundantly represented here ; 

 the genera Lagothrix, Pithetia, Brachyurus, Brachy teles (Eriodes), 

 and Callithrix being restricted to it. Among the forms that are 

 unrepresented, may be mentioned guanacos and vicunas (Lama), 

 viscachas (Lagostomus), the Patagonian cavy (Dolichotis), and 

 chinchillas (Eriomys and Lagidium). 



The Mexican or Central American sub-region differs chiefly 

 from the last by the paucity of the essentially Neotropical forms, 

 and the large mingling of Arctogaeic types ; among the latter, 

 the shrews (Soriridce), a pouched rat (Heteromys}^ and the caxo- 

 mistle (Bassariscus) being noticeable. In the Chilian sub-region 

 marmosets, monkeys, sloths, tapirs, and peccaries are wanting; 



1 According to Senor Figueira it just enters Uruguay. 



