CHAP. XIV.] 
THE NEOTROPICAL REGION. 
5 
number of groups to which verdant forests are essential, can be 
traced to the unsuitable conditions rather than to the existence 
of the mountain barrier. All Tropical South America, therefore, 
is here considered to form but one sub-region. 
The portion of North America that lies within the tropics, 
closely resembles the last sub-region in general zoological features. 
It possesses hardly any positive distinctions; but there are several 
of a negative character, many important groups being wholly 
confined to South America. On the other hand many genera 
range into Mexico and Guatemala from the north, which never 
reach South America ; so that it is convenient to separate this 
district as a sub-region, which forms, to some extent, a transition 
to the Nearetic region. 
General Zoological Features of the Neotropical Region. — Rich- 
ness combined with isolation is the predominant feature of 
Neotropical zoology, and no other region can approach it in 
the number of its peculiar family and generic types. It has 
eight families of Mammalia absolutely confined to it, besides 
several others which are rare elsewhere. These consist of two 
families of monkeys, Cebidse and Hapalidse, both abounding in 
genera and species ; the Phyllostomidae, or blood-sucking bats ; 
Chinchillidee and Caviidse among rodents; besides the greater 
part of the Octodontidse, Echimyidse and Cercolabidse. Among 
edentata, it has Bradypodidee, or sloths, Dasypodidse, or armadillos, 
and Myrmecophagidse, or anteaters, constituting nearly the entire 
order ; while Procyonidas, belonging to the carnivora, and Didel- 
phyidse, a family of marsupials, only extend into the Nearctic 
region. It has also many peculiar groups of carnivora and of 
Muridse, making a total of full a hundred genera confined to the 
region. Hardly less remarkable is the absence of many wide- 
spread groups. With the exception of one genus in the West 
Indian islands and a Sorex which reaches Guatemala and Costa 
Rica, the. Insectivora are wholly wanting ; as is also the extensive 
and wide-spread family of the Yiverridse. It has no oxen or 
sheep, and indeed no form of ruminant except deer and llamas ; 
neither do its vast forests and grassy plains support a single form 
of non-ruminant ungulate, except the tapir and the peccary. 
