44 2 ZOOLOGY. 



mammae are posterior. Hair is very scant, but the layer of 

 fat or " blubber " beneath the skin is very thick, and serves as 

 a non-conductor of heat. 



The whales are the largest living animals. The largest of 

 these, the Greenland whale, may attain a length of seventy-five 

 feet or more. It must be remembered that the whales are air- 

 breathers, and therefore must come to the surface to breathe 

 or " blow." The Cetacea prey on the smaller swimming or 

 floating animals found in the ocean, as fish, squid, Crustacea, 

 etc. Whales are principally sought for their fat and baleen, 

 or whale-bone. 



Order 4. Ungulata (hoofed animals}. This order in- 

 cludes a great number of animals, chiefly herbivorous, that 

 walk on their toes. In these forms the horny growth which 

 we have so frequently found in vertebrates at the end of the 

 digits takes the form of a hoof. Toes are usually not more 

 than four in number. The canine teeth are small or absent. 

 The following suborders are important. 



Suborder (a) Artiodactyla (even-toed}. These are ungu- 

 lates with toes reduced to four or two. The third and fourth 

 toes persist and bear the weight of the animal, and the second 

 and fifth, if present, may or may not touch the ground. The 

 mammae are distributed along the entire abdomen or are con- 

 fined to the pelvic region. The ruminants, as the ox, the 

 carriel, sheep and deer, and the non-ruminants, as the swine 

 and the hippopotamus, are representatives of the group. Here 

 belong some of man's most useful food-animals. 



Suborder (b) Perissodactyla (odd-toed). These are 

 characterized by the fact that the weight of the body rests on 

 the third or middle toe, the others being more or less reduced. 

 The stomach is simple. No proboscis. The mammae are few 

 and confined to the pelvic region. The most common exam- 

 ples are the horse and its allies, in which the third is the only 

 digit, and the rhinoceros, which has the second and fourth, as 

 well. It is known that the remote ancestors of the horse had 

 a second and a fourth toe where only splints occur now, and 



