134 ORDERS CETACEA, RODENTIA, AND EDENTATA. 



adapted to their habits. Some of these, as the Seal, pass a 

 large portion of their time in the water, and have the extremi- 

 ties formed for swimming ; and these naturally lead us, there- 

 fore, towards the next order. 



VI. CETACEA, orjfisk-like Mammals ; which are distinguished 

 from all ordinary mammalia by the absence of the posterior 

 extremities, and by the conversion of the anterior into swim- 

 ming paws or paddles. Of the animals thus adapted to the 

 life of Fishes, however, those only are included in this order 

 which are carnivorous in their habits, and whose alimentary 

 canal is formed to digest animal food. 



123. The unguiculated Mammals which do not possess the 

 three kinds of teeth, are divisible into two orders, which exhibit 

 the unguiculated structure in its lowest grade. 



VII. RODENTIA, or gnawing animals ; a group very easily 

 distinguished by the peculiar conformation of the front teeth, 

 which are two in each jaw, very strong, with sharp cut- 

 ting edges, and constantly growing at the roots ; thus forming 

 admirable instruments for gnawing. Of this group, the Squirrel, 

 Rat, Beaver, &c., are examples. These front teeth are really to 

 be regarded as the canines ; the incisors being altogether absent, 

 so as to allow them to come together on the central line. The 

 number of molars is variable ; but they are all formed with 

 ridges of enamel, placed more or less transversely to the jaw. 



VIII. EDENTATA, or toothless animals ; a term which is not 

 altogether correct, but which serves to express the character of 

 a large proportion of the order designated by it. This group is 

 properly characterised by the entire absence of front teeth in 

 both jaws ; and in the Ant Eaters, &c., there are no teeth 

 whatever; whilst the Sloths are possessed of molar teeth, 

 though of very imperfect formation. 



1 24. The ungulated, or hoofed Mammals, are easily subdi- 

 vided into two orders, by the presence or absence of the rumi- 

 nating faculty, and of the peculiar conformation which apper- 

 tains to it ( 98). 



IX. RUMINANTIA, or ruminating animals ; a group which 

 is composed of the Ox, Sheep, Antelope, Camel, and other well- 



