MAMMALIA. 43 



TRIBE IV. MACROPUS, SHAW. KANGAROO. 



No canines ; legs of unequal height, the hinder ones the 

 longest ; tail short, muscular and serving as an organ of sup- 

 port and locomotion. 



TRIBE V. KOALA, Cuv. 



Two long incisives in the under jaw ; in the upper jaw two 

 long incisives in the middle, small ones upon the sides, and 

 two small canines. No tail. 



TRIBE VI. PHASCOLOMES. POUCHED RATS. 



True Rodentia in the teeth and intestines ; no tail ; form 

 clumsy ; body as if crushed ; head large and flat ; legs short ; 

 claws long and fit for digging ; graminivorous. 



ORDER V. RODENTIA. 



In each jaw two large incisors, increasing during life, and 

 of prismatic form; the enamel being concentrated to the front. 

 No canines; molars with flat crowns, whose enamelled emi- 

 nences are always transverse. Under jaw articulated by a 

 longitudinal condyle, so as to have no horizontal movement 

 except from behind to before, and vice-versa, as is suitable 

 for the action of gnawing. Carriage behind, in general, higher 

 than before, making these animals leapers ; intestines very 

 long ; stomach simple or little divided ; caecum very volumi- 

 nous ; brain nearly smooth, and without convolutions ; eyes 

 directed sideways, large in the nocturnal species, and dimi- 

 nishing as the habit is more subterranean ; forearms have but 

 little power of rotation, and the two bones are often united. 

 Six remarkable genera. 



GENUS I. SCIURTJS, Lin. Squirrel. 



Inferior incisors strongly compressed ; tail long and well 

 furnished with hair ; four toes before and five behind ; head 

 broad ; eyes projecting and lively ; clavicles complete. Two 

 subgenera. 



