80 GEOGRAPHICAL DISTRIBUTION. 



those of any other region, with perhaps the exception of the Hoi- 

 arctic. According to Giinther they comprise nearly seven hundred 

 distinct forms, although representing only nine families. About 

 one-third of the species belong to the family Characinidae, and 

 a somewhat larger number to the cat-fishes (Silurida?). The 

 toothed-carps (cyprinodonts) are represented by sixty or more 

 species. Among the distinctive fishes of the region are the 

 electric eel (Gymnotus electricus), from the equatorial regions, 

 and the remarkable lung-fish (Lepidosiren paradoxa) of the Ama- 

 zon. 



The Neotropical tract may be conveniently divided into the 

 following sub-regions: 1, the Brazilian, comprising Brazil, Guiana, 

 Venezuela, Colombia, Ecuador, Paraguay, and the cis- Andean por- 

 tions of Peru and Bolivia, inclusive of the eastern slope of the 

 mountain-axis, essentially a region of dense and luxuriant forests ; 

 2, the Chilian, principally a region of open plains and pampas, 

 comprising Chili, Patagonia, the Argentine Republic, Uruguay, 

 and the remaining parts of Peru and Bolivia, extending to about 

 the fourth parallel of south latitude; 3, the Mexican, including 

 the Isthmus of Panama, Central America, and Southern Mexico ; 

 and, 4, the Antillean, or the sub-region of the West India Isl- 

 ands. In the first of these sub-regions, the Brazilian, the faunal 

 facies is essentially that of the Neotropical realm taken as a whole, 

 inasmuch as there is scarcely a single group of important or typical 

 South American animals which has not its representatives here. 

 Furthermore, the majority of these forms have their greatest de- 

 velopment in this tract. Among its most distinctive negative 

 elements may be cited the chinchillas, the spectacled bear, the 

 llamas (with the alpaca, vicufla, and guanaco), the rheas (South 

 American ostriches), and the condor members of the fauna of 

 the Chilian sub-region which are either wholly wanting, or but 

 barely pass beyond the regional confines. Positive distinguishing 

 characters among the Mammalia may be found in the special de- 

 velopment of the quadrumanous and edentate types among the 

 former, in addition to the more widely distributed forms, such as 

 Cebus, Ateles (spider-monkey), and Mycetes (howler), the woolly- 

 monkeys (Lagothrix), the sakis (Pithecia), the douroucoulis or 

 night-monkeys (Nyctipithecus), squirrel-monkeys (Chrysothrix), and 

 some thirty or more species of marmosets, which appear to be con- 



