TEETH OF QUADRUMANA. 149 



each jaw, generally very long, and having the 

 exact shape of a chisel ; and the molar teeth 

 have surfaces, irregularly marked with raised 

 zig-zag lines, rendering them very perfect in- 

 struments of trituration. The zygomatic arch is 

 exceedingly slender and feeble ; and the condyle 

 is lengthened longitudinally to allow of the jaw 

 being freely moved forwards and backwards, 

 which is the motion for which the muscles are 

 particularly adapted, and by which the grinding 

 operation is performed. The Beaver, the Rat^ 

 the Marmot, and the Porcupine, present examples 

 of this structure, among the omnivorous rodentia : 

 and the Hare, the Rabbit, the Squirrel, among 

 those which are principally herbivorous. 



The Quadrumana, or Monkey tribes, approach 

 nearest to the human structure in the confor- 

 mation of their teeth, which appear formed for 

 a mixed kind of food ; but are especially 

 adapted to the consumption of the more esculent 

 fruits. The other orders of Mammalia exhibit 

 intermediate gradations in the structure of their 

 teeth to those above described, corresponding to 

 greater varieties in the nature of their food. Thus 

 the teeth and jaws of the Hycena are formed 

 more especially for breaking down bones, and 

 in so doing exert prodigious force ; and those of 

 the Sea Otter have rounded eminences, which 

 peculiarly fit them for breaking shells. 



The teeth, though composed of the same 



