10 INTRODUCTORY. [CHAP. 



or amphibians as their standards. Between birds and mammals, 

 as might have been expected from the comparatively recent high 

 development of these groups, there is much greater accord. 

 Birds, however, differ from mammals (with the exception of bats) 

 in their power of flight, which enables many of them to cross 

 wide ocean-tracts, and therefore renders them less valuable as 

 indicative of the changes that have taken place in the distribution 

 of land and water than the latter, which, as a rule, require 

 direct means of land transit for their wanderings. 



Excluding man (and for the most part bats) and likewise the 



aquatic forms, such as seals, whales, and porpoises, 



o/ Mamma" niammals are the animals best adapted for parcelling 



in Geographi- out the globe into zoological provinces for two chief 



cal Distribu- 3 _. . , r , . , , 



tion. reasons. Firstly, they form a group which only at- 



tained its maximum development at a comparatively 

 late epoch of the earth's history; and, secondly, their movements 

 are mainly limited by the extent of the land-surfaces of the globe 

 which were in actual communication at the time of such migra- 

 tions. Consequently they afford the safest and truest indications 

 of the latest changes which have taken place in the distribution 

 of land and water. 



As reference in the following pages will constantly have to be 



. fi made to the various groups of mammals, it will be 



tion of Mam- well to give a list in this place of the chief ordinal 



and subordinal groups into which the class is 



divided ; such as are now extinct being indicated by an asterisk. 



The list stands as follows, viz. : 



i. Order PRIMATES. Apes, Monkeys, and Lemurs. 



1 Suborder ANTHROPOIDEA. Apes and Monkeys. 



2 LEMUROIDEA. Lemurs. 



ii. Order CHIROPTERA. Bats. 



1 Suborder MEGACHIROPTERA. Fruit-bats. 



2 ,, MICROCHIROPTERA. Insectivorous Bats. 



iii. Order INSECTIVORA. Insectivores. 



1 Suborder DERMOPTERA. Flying-Lemurs. 



2 ,, INSECTIVORA VERA. Shrews, Moles, 



Hedgehogs, etc. 



