43 o DISTRIBUTION IN SPACE AND TIME 



The Odd -toed Ungulates (Perissodactyla) are only represented 

 by the archaic Tapirs (Tapirus) of South and Central America. 

 They are one of the stock examples of discontinuous distribution, 

 being also found in south-east Asia. As in many similar cases 

 they are the last surviving representatives of a once widely dis- 

 tributed group (compare p. 410). There is also a scarcity of 

 Even-toed Ungulates (Artiodactyla), for of non-ruminants there 

 are only the little Peccaries (Dicotyles], "which differ in many 

 ways from the Swine of the Old World. They also range into 

 the south of the Nearctic region. Among the Ruminants or 

 Cud-Chewers (Ruminantia) the Deer Family (Cervidce) is repre- 

 sented by a number of species belonging to two genera exclusively 

 American. One of these (Padus) only includes a very small 

 form (P. humilis], native to the Chilian Andes, and of which the 

 male possesses tiny spikes by way of antlers. Most of the 

 species belonging to the other genus (Cariacus) are restricted to 

 the Neotropical region, but the largest forms, e.g. Virginian and 

 Mule Deer, which also have the most complex antlers, are 

 Nearctic. The large family (Bovida) embracing Sheep, Goats, 

 Antelopes, and Oxen, which has but few representatives in the 

 Nearctic region, here has none at all. The Camels of the Old 

 World are also absent, but the Guanaco (Lama guanacus) and 

 Vicunia (L. vicunia) belong to the same family (Camelidce], and 

 furnish another typical example of discontinuous distribution. 



Gnawers (Rodentia) are extremely numerous in the Neotro- 

 pical region, and among peculiar forms may be noted the Cavies 

 (Caviida\ which include the largest existing Rodent (Hydro- 

 chcerus capybara], the Agoutis {Dasyproctidcz), and the Chinchillas 

 (Ckinckillida). The archaic and decadent order of Mammals 

 Poor in Teeth (Edentata) is also better represented here than 

 anywhere else, for typical Ant-eaters (Myrmecophagida), Sloths 

 (Bradypodidcz), and Armadilloes (Dasypodidcz) are only to be 

 found in South America. As to Pouched Mammals (Marsu- 

 pialia\ the Opossums (Didelphyidce) are native to both Americas, 

 while the Opossum Rats (Ccenolestes) belong to Colombia and 

 Ecuador. 



Neotropical Birds (Aves). The region stands unsurpassed 

 for the richness and variety of its avifauna, while a great many 

 families and genera are represented nowhere else, and some of 

 the most distinctive forms are only shared with the Nearctic area. 



