CHORDATA 



375 



have a longer and sharper snout. The bay porpoise lives along 

 the shores and in the mouths of rivers, and is one of the small- 

 est of the Cetacea, rarely exceeding a meter and a half in 

 length. The dolphin, Delphinus delphis (Fig. 367), is abundant 

 in the Mediterranean, along the western coast of Europe, and 

 in the warmer portions of the Atlantic ; they are often seen in 



FlG. 367. Delphinus delphis, the common dolphin. (From Claus and Sedgwick's Text- 

 book.) 



considerable numbers, leaping in graceful curves from the water. 

 The largest toothed whale is the sperm whale, Physeter macro- 

 cephalus ; the male may attain a length of twenty-five meters; 

 its teeth are confined to the lower jaw ; the head is very large, 

 about a third of the total length of the body. The sperm whale 

 is extensively hunted, not only for its blubber, but also for the 

 liquid oil and spermaceti which are found in a large cavity in 

 the head. It is found in all oceans which are not icy, being 

 more abundant in the southern hemisphere. Its food consists 

 largely of Cephalopoda, and under certain conditions undigested 

 squids become concretionary in the intestines and form the 

 ambergris largely used by the perfumers. 



The toothless whales never have functional teeth in the adult, 

 and are known commonly as the baleen or whalebone whales, 

 because the upper jaw is provided with many rows ot vertical, 

 horny plates with fringed edges; there are usually many hundred 

 such plates (Fig. 36S). These supply the whalebone of com- 

 merce, and during life are used by the animal in securing its 

 food. It swims along with open mouth, taking in large quanti- 

 ties of pelagic Crustacea and Mollusca, and then, closing its 

 mouth, the water is forced out between the fringes, and the 

 captured animals, held as in a sieve, are thus swallowed. ( )n 

 the western coast of North America the California gray whale 



