176 ZOOLOGICAL GEOGRAPHY. [PART III. 
agencies in the limitation of their range. Even among the 
aerial bats, however, only one family—the Vespertilionide—is 
truly cosmopolitan, the others having a more or less restricted 
range. Neither are the Cetacea necessarily cosmopolitan, most of 
the families being restricted either to warm or to cold seas ; but 
one family, the dolphins (Delphinidse), is truly so. This order 
however will not require further notice, as, being exclusively 
marine the groups do not enter into any of our terrestrial 
regions. The only other family of mammals that may be con- 
sidered to be cosmopolitan, is the Muride (rats and mice); yet 
these are not entirely so, since none are known to be truly 
indigenous in any part of the Australian region except Australia 
itself. FE 
In the class of Birds, a number of families are cosmopolites, 
if we reckon as such all which are found in each region and 
sub-region ; but several of these are so abundant in some parts, 
while they are so sparingly represented in others, that they 
cannot fairly be considered so. We shall confine that term 
therefore, to such as, there is reason to believe, inhabit every 
important sub-division of each region. Such are, among the 
Passerine birds the crows (Corvide), and swallows (Hirundi- 
nid) ; among the Picariz the kingfishers (Alcedinide) ; among 
other Land birds the pigeons (Columbide), grouse and partridges 
(Tetraonidz), hawks (Falconide), and owls (Strigide) ; among 
the Waders the rails (Rallide), snipes (Scolopacide), plovers 
(Charadriadz), and herons (Ardeide); and among the Swimmers 
the ducks (Anatidz), gulls (Laride), petrels (Procellariide), 
pelicans (Pelecanide), and grebes (Podicipide). 
In the class of Reptiles there are few absolutely cosmopolitan 
families, owing to the scarcity of members of this group in some 
insular sub-regions, such as New Zealand and the Pacific Islands. 
Those which are most nearly so are the Colubride among snakes. 
and the Scincide among lizards. 
There is no cosmopolitan family of Amphibia, the true frogs 
(Ranidz) being the most widely distributed. 
Neither is any family of Freshwater Fishes cosmopolitan, 
the Siluride, which have the widest range, being confined 
