CHAP. XIV.] THE NEOTROPICAL REGION. 5 



nuinber 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 Nearctic region. 



General Zoological Features of the Neotropical Region. — Eich- 

 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, Cebidae and Hapalidae, both abounding in 

 genera and species ; the Phyllostomidse, or blood-sucking bats ; 

 Chinchillidae and Caviidse among rodents ; besides the greater 

 part of the Octodontidse, Echimyidae and Cercolabidse. Among 

 edentata, it has Bradypodidce, or sloths, Dasypodidse, or armadillos, 

 and Myrmecophagidse, or anteaters, constituting nearly the entire 

 order ; while Procyonidse, 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 

 Eica, the Insectivora are wholly wanting ; as is also the extensive 

 and wide-spread family of the Viverridse. 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. 



