6 
ZOOLOGICAL GEOGRAPHY. 
[part III. 
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 : Caerebidse, or 
sugar-birds ; Phytotomidae, or plant-cutters ; Pipridae, or mana- 
kins ; Cotingidae, or chatterers ; Pormicariidae, or ant-thrushes ; 
Dendrocolaptidse, or tree-creepers j Pteroptochidae ; Rhamphas- 
tidae, or toucans ; Bucconidae, or puff-birds ; Galbulidae, or jaca- 
mas; Todidae, or todies; Momotidae, or motmots; Steatornithidae. 
the guacharo, or oil-bird ; Cracidae, or curassows ; Tinamidae, or 
tinamous ; Opisthocoraidae, the hoazin ; 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 liang-nests ; Tyrannidae, or tyrant-shrikes ; 
Trochilidae, or humming-birds ; and Conuridae, or macaws. Most 
of these families abound in genera and species, and many are of 
immense extent ; such as Trochilidae, with 115 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 
