CHAP. XIV.] 
THE NEOTROPICAL REGION. 
7 
species, have the prehensile tail, the remainder having this organ 
either short, or lax as in the Old World monkeys. Other dif- 
ferences from Old World apes, are the possession of a broad nasal 
septum, and a less opposable thumb ; and the absence of cheek- 
pouches, ischial callosities, and a bony ear-tube. The Hapalidse, 
or marmozets, agree with the Cebidse in all these characters, but 
have others in addition which still more widely separate them from 
the Simiidee; such as an additional premolar tooth, acute claws, and 
thumb not at all opposable ; so that the whole group of American 
monkeys are radically different from the remainder of the order. 
The Procyonkke are a distinct family of Carnivora, which make 
up for the scarcity of Mustelidse in South America, The Suidte 
are represented by the very distinct genus Dicotyles (Peccary) form- 
ing a separate sub-family, and differing from all other genera in 
their dentition, the absence of tail and of one of the toes of the 
hind feet, the possession of a dorsal gland, and only two mammas. 
The rodents are represented by the Chinch illidse and Caviicko, 
the latter comprising the largest animals in the order. The 
Edentata are almost wholly confined to this region ; and the three 
families of the sloths (Bradypodidee), armadillos (Dasypodidse), 
and ant-eaters (Myrmecopliagidee), are widely separated in struc- 
ture from any Old World animals. Lastly, we have the opossums 
(Didelphyidse) , a family of marsupials, but having no close affi- 
nity to any of the numerous Australian forms of that order. 
We have already arrived at the conclusion that the presence of 
marsupials in South America is not due to any direct transfer- 
ence from Australia, but that their introduction is comparatively 
recent, and that they came from the Old World by way of North 
America (vol. i., p. 155). But the numerous and deep-seated 
peculiarities of many other of its mammalia, would indicate a 
very remote origin; and a long-continued isolation of South 
America from the rest of the world is required, in order to account 
for the preservation and development of so many distinct groups 
of comparatively low-type quadrupeds. 
Distinctive Characters of Neotropical Bi rds . — The birds which 
are especially characteristic of this region, present similar 
distinctive features. In the enormous group of Passerine 
