6 ZOOLOGICAL GEOGRAPHY. [PART m. 



Birds. In birds, the Neotropical region is even richer and more 

 isolated. It possesses no less than 23 ] families wholly confined 

 within its limits, with 7 others which only extend into the Nearc- 

 tic region. The names of the peculiar families are : Qserebidse, or 

 sugar-birds ; Phytotoinidae, or plant-cutters ; Pipridae, or inana- 

 kins ; Cotingidae, or chatterers ; Formicariidae, or ant-thrushes ; 

 Dendrocolaptidae, or tree-creepers ; Pteroptochidae ; Bhamphas- 

 tidae, or toucans ; Bucconidae, or puff-birds ; Galbulidae, or jaca- 

 mas; Todidae, or todies; Momotidse, or motmots; Steatornithidae. 

 the guacharo, or oil-bird; Cracidae, or curassows; Tinamidae, or 

 tinamous ; Opisthocomidae, the hoazin j Thinocoridae ; Cariamidae ; 

 Aramidae; Psophiidae, or trumpeters ; Eurypygidae, or sun-bitterns; 

 and Palamedeidae, or horned-screamers. The seven which it 

 possesses in common with North America are: Vireonidae, or 

 greenlets ; Mniotiltidae, or wood-warblers ; Tanagridae, or tana- 

 gers; Icteridae, or hang-nests; Tyrannidae, or tyrant-shrikes; 

 Trochilidae, or humming-birds ; and Cgnuridse, or macaws. Most 

 of these families abound in genera and species, and many are of 

 immense extent ; such as Trbchilidae, with 11 fr^genera, and nearly 

 400 species ; Tyrannidae, with more than 60 genera and nearly 

 300 species ; Tanagridae, with 43 genera and 300 species ; Den- 

 drocolaptidae with 43 genera and more than 200 species ; and 

 many other very large groups. There are nearly 600 genera 

 peculiar to the Neotropical region ; but in using this number as 

 a basis of comparison with other regions we must remember, that 

 owing to several ornithologists having made the birds of South 

 America a special study, they have perhaps been more minutely 

 subdivided than in the case of other entire tropical regions. 



Distinctive Characters of Neotropical Mammalia. It is im- 

 portant also to consider the kind and amount of difference 

 between the various animal forms of this region and of the 

 Old World. To begin with the Quadrumana, all the larger 

 American monkeys (Cebidae) differ from every Old World group 

 in the possession of an additional molar tooth in each jaw ; and 

 it is in this group alone that the tail is developed into a prehen- 

 sile organ of wonderful power, adapting the animals to a purely 

 arboreal life. Four of the genera, comprising more than half the 



