1 82 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



may be said that the order includes all quadrupeds 

 having separate, clawed toes and no incisors. The 

 sloths are arboreal ; the others burrow. The brain is 

 generally smooth ; but that of the ant-eater is convoluted, 

 and has a large corpus callosum ; but in all the cerebel- 

 lum and part of the olfactory lobes are exposed. 



FIG. 169. Armadillo (Dasypus). Copyright, 1901, by N.Y. Zoological Society. 



2. Cetacea, or whales, have the form and life of fishes, 

 yet they possess a higher organization than the preceding 

 orders. They have a broad brain, with many and deep 

 foldings ; the foramen magnum of the skull is entirely 

 posterior ; the whole head is disproportionately large, and 

 the jaws greatly prolonged. The body is covered with a 

 thick, smooth skin, with a layer of fat (" blubber ") under- 

 neath ; there are no clavicles ; the hind limbs are want- 

 ing, and the front pair changed to paddles (Fig. 171); 

 the tail expands into a powerful, horizontal fin ; neck 

 and external ears are wanting ; the eyes small, with only 

 two lids ; the nostrils (blowholes) double in the whale, 



