74 GEOGRAPHICAL DISTRIBUTION. 



ing not only the deep lowlands, but also the mountain-slopes to a 

 very considerable elevation. Commencing on the Atlantic border, 

 it stretches, through a north and south extent of thirty degrees of 

 latitude, almost unbroken for nearly three thousand miles to the 

 base of the Andes, harbouring in its dense recesses a host of the most 

 varied animal forms. Beyond, and partially enclosed within, the 

 limits of this vast forest region are the various forms of pasture- 

 land, or grassy plains, the llanos or savannas of Venezuela, the 

 campos of the highlands of Brazil, and the pampas of the Argen- 

 tine Republic and Patagonia. In the great Andean chain, which 

 traverses in one continuous sweep the entire north and south ex- 

 panse of the region, we have all the more characteristic features of 

 a mountain-system developed on a most gigantic scale — high pla- 

 teaus, deep valleys, wooded and barren slopes — conditions affecting 

 in a most marked degree the diversity of its animal and vegetable 

 creations. Desert areas, or such as are rendered almost unfit for 

 habitation by reason of extremes of climate, like the north of both 

 the North American and Eurasiatic continents, are, if we except 

 the most elevated mountain-summits, limited to a few scattered 

 pCvtches of small area in tlie Argentine Republic, and to a narrow 

 tract of littoral lying in Peru and Chili, on the Pacific side of the 

 mountain-axis. 



Zoological Characters of the Neotropical Realm.— In com- 

 paring the fauna of the Neotropical with that of the other zoogeo- 

 graphical regions we are struck with two things: 1, its extraordi- 

 nary richness ; and 2, the very great preponderance of forms that are 

 peculiar to the region and not met with anywhere else. According 

 to Wallace, the region comprises no less than forty-five families and 

 nine hundred genera of vertebrate animals which are strictly pe- 

 culiar to it, while it has representatives of one hundred and sixty- 

 eight out of the total of about three hundred and thirty families 

 recognised by naturalists ; in other words, more than one-half of 

 all the families scattered over the globe are here represented. Of 

 about thirty-one mammalian families eight are almost completely 

 confined to the region, as follows: The Cebidae, or true South 

 American monkeys; the Hapalidse, or marmosets; the Phyllosto- 

 midaj, or simple leaf-nosed bats, which include the vampires (with 

 one extra-limital species in California) ; the Chinchillidse, compris- 

 ing the chinchilla and vizcacha, a small group of animals confined 



