100 CLASS MAMMALIA. 



Rat, extremely small and imperfect; the eye pupil is in some- 

 species round, and in others elongated horizontally; the nos- 

 trils are pierced at the extremity of the muzzle, which is 

 longer than the jaws ; the tongue is soft ; the ears are in 

 some, as the Hares, very much developed, and in others, as 

 the Mole Rat, altogether wanting. They are in general 

 well covered with hair, except on the toes, extremity of the 

 muzzle, and sometimes the tail, and a few have spines either 

 round or flattened. Some, as the Squirrels, have the toes 

 deeply divided ; others, as the Hydromys and the Castor, are 

 palmated, and some are capable of flight by means of lateral 

 membranes extended from the anterior to the posterior 

 extremities, and attached to the sides. 



Their locomotion varies, but is most generally planti- 

 grade. Some of them are rapid runners ; others, the 

 Gerboas and Gerbilli, great leapers ; a few have subter- 

 raneous habits and physicalities, as the Mole Rat; and 

 several of them, the Squirrels, fyc. are fitted for living in 

 trees. Their nails are proper to each of these varied 

 modes of existence. 



The tail, though apparently of inferior importance in the 

 destinies of the species, varies considerably among the 

 Rodentia. The Castor has it naked and flat, the Rat 

 slightly ridged crosswise, the Ondatra compressed, the 

 Squirrel feathery, and the Gerboa tufted at the end. 



Some of the Rodentia are more decidedly herbivorous 

 than others which approach the omnivorous character. 

 Their intestines are generally long; the stomach simple, or 

 only partially divided; the caecum large, except in the 

 Myoxus, a very carnivorous genus, which is totally destitute 

 of this viscera. 



Some of the Rodentia are exceedingly destructive to the 

 industry and property of mankind, as the Hamsters, Field 

 Mice, Rats, Mice, fyc. ; but others administer to our appetite 

 or comfort, as, of the former description, the Hare, Rabbit, 



