Mammalia: Skin, Muscles, Skeleton 



603 



Fig. 466. Mammalian profiles. (Top) Lion (carnivore) and rat (rodent). [Bottom) 

 Solenodon (insectivore) and chimpanzee (primate). (Top, courtesy, American 

 Museum of Natural History, New York. Bottom, courtesy, Museum of Compara- 

 tive Zoology, Harvard University.) 



proportions of the brain-case. It follows, then, that the shape of a skull, 

 and therefore that of the animal's head, depends largely on two factors: 

 the degree of development of the brain, and the length of the nasal 

 region. Usually long "snouts" go with small brains, but there are 

 exceptions. 



In a small-brained mammal, the skull is usually long, narrow, 

 shallow, and flat or only slightly convex on top. The distance between 

 ear and eye is usually less than the distance from eye to tip of snout. 

 With increase in size of brain, the rear part of the skull expands both 

 laterally and upward. If the increase is considerable, the rear part of 



