400 VERTEBRATE ZOOLOGY 



divided not the hoof" is without foundation on either count; for 

 they are not ruminants, and there are four hoofs in front and three 

 behind. 



Section D. Cetacea (Whales and Dolphins) 



This assemblage of large aquatic mammals is profoundly modified 

 for marine life. They are unquestionably the most highly specialized 

 structurally of all mammals, although certain of their characters are 

 persistently primitive. In older classifications they have usually 

 been placed among the earlier orders, because they are least like 

 Man, who was looked upon as the ultimate goal of organic evolution. 

 Is it too serious a blow to human complacency to have to cede the 

 honor of being placed at the top of the systemic ladder to the whales? 

 The statement that the whales are the most highly specialized mam- 

 mals is backed up by the following criteria of specialization: 1, the 

 whales are farthest removed from the generalized types of mammals in 

 all of their adaptive characters; 2, they have undergone losses of such 

 typical mammalian structures as hair, teeth (in some groups), claws, 

 and hind limbs; 3, the skeleton of the fore limbs is progressively spe- 

 cialized by the addition of several digits; 4, they have reached a size 

 unrivaled in the world's history, far surpassing that of the giant 

 reptiles of Mesozoic times; 5, the stomach is one of the most com- 

 plex among mammals; 6, the skull of some of the whales is the most 

 asymmetrical and otherwise specialized among mammals. 



Three orders of Cetacea are distinguished: Zeuglodontia (extinct 

 generalized whales), Odontoceti, and Mystacoceti. 



Order 14. Odontoceti (Toothed Whales). — This order includes 

 the sperm whales, narwhals, beaked whales, porpoises and dolphins. 

 They are characterized by the presence of teeth and absence of whale- 

 bone; by the possession of a single nostril or blow hole; by asym- 

 metry of the skull; and by having some of the ribs two headed. 



The sperm whale or cachalot (Fig. 207, C), Physeter, is probably 

 the largest animal that ever lived, and the writer was fortunate enough 

 to have been able to examine and to record the measurements of 

 what is now beUeved to have been the largest specimen ever authen- 

 tically described. This was the well-known Port Arthur whale, that 

 came ashore on the north coast of the Gulf of Mexico in March, 1910. 

 This animal measured on a straight line from snout to end of flukes 

 (not following curvatures as is usually done) sixty-three and a half 



