302 COMPARATIVE ZOOLOGY. 
ing. The lower jaw has longitudinal condyles, which 
work freely backward and forward in longitudinal fur- 
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Fig. 326.—Incisor Teeth of the Hare. 
rows. Nearly all have clavicles; and the toes are clawed. 
The cerebrum is nearly or quite smooth, and covers but a 
small part of the cerebellum. All are vegetarian. 
About two-thirds of all known Mammals are Rodents. 
They range from the equator to the poles, over every con- 
tinent, over mountains and plains, deserts and woods. The 
Fia. 327.—Beaver (Castor Canadensis). North America. 
more important representatives are the Porcupines, Capy- 
baras, Guinea-pigs, Hares, Mice, Rats, Squirrels, and Bea- 
vers. The Capybara and Beaver are the giants of the 
race. 
