MAMMALS. 379 



variously interpreted as a part of the pelvis or as the bone 

 of the thigh. The body terminates in a bilobed caudal 

 fin ('flukes'), but this, instead of being vertical, as in the 

 fish, is horizontal. All of the whales have teeth in the 

 young stages; some retain them through life, while others 

 lose them long before maturity, sometimes even before 

 birth. The stomach is remarkable for having several 

 (4-7) chambers, this complication recalling the condition 

 in the cow (see p. 385). 



According to the presence or absence of teeth the living 

 w r hales are divided into two groups. In some of the 

 toothed whales but two teeth are present; others may 

 have a large number; and usually these cannot be well 

 distributed among incisors, canines, etc., as all are essen- 

 tially alike in size and shape. In the male narwal, how- 

 ever, one of the upper teeth on one side (apparently a 

 canine) grows straight forward into a long twisted spear 

 eight or nine feet in length, while the other teeth disap- 

 pear at an early age. The killer-whales are compara- 

 tively small, but are among the most voracious of mam- 

 mals, not hesitating to attack the largest whales. Here 

 also belong the blackfish, porpoises, and dolphins. The 

 sperm-whales are larger, and have no teeth in the upper 

 jaw r , while the low^er jaw is abundantly supplied. They 

 derive their common name from the spermaceti which 

 they produce. This is a solid granular substance found 

 in the 'case/ a cavity occurring on the right side of the 

 front of the head between the skin and the skull. The 

 sperm-whales also produce the substance known as am- 

 bergris used in perfumery. This is a concretion formed 

 in the intestine and is found floating on the surface of 

 the sea. It is worth about $20 a pound. 



The toothless whales are also known as whalebone whales, 



