36 



organs for fliglit, just as the Dugongs and Manatees are asso- 

 ciated with the Cetacea on account of their resemblance to Fishes 

 arising out of the same modification of the locomotive system for 

 an aquatic existence. The herbivorous Cetacea are now separated 

 from the piscivorous Cetacea as a distinct order ; and with almost 

 as good reason we might separate the frugivorous from the in- 

 sectivorous Cheiroptera ; the cases are very nearly parallel. 



Nature, in short, is not so rigid a systematist as Man. There 

 are peculiar conditions of existence which she is pleased shall be 

 enjoyed by peculiarly modified mammals ; these peculiarities break 

 through the rules of structure which govern the majority of species 

 existing and subsisting under the more general conditions of ex- 

 istence, to which the larger groups of Mammalia are respectively 

 adjusted. 



One class of organs seems to govern one order, another class 

 another order ; the dental system, which is so diversified in the 

 Marsupialia and JBruta, is as remarkable for its degree of con- 

 stancy in the Bodentia and Insectivora. But, as a general rule, 

 the characters from the dental, locomotive, and placental systems 

 are more closely correlated in the Gryrencephalous orders than in 

 those in the inferior subclasses of the Mammalia. 



In the subjoined tabular view of the classification of the Mam- 

 malia, the groups below the ranks of orders are inserted merely as 

 illustrations of those orders, not as equivalent subdivisions, or as 

 the most natural subdivisions of those orders, into which it has 

 not been the aim of the present paper to enter. 



