176 



MAMMALIA— ORDER VIIL—CETACEA. 



crests behind the nasal aperture. All these cetaceans are entirely pelagic in 

 their habits, and feed exclusively or chiefly on cuttles and squids. In the 

 sperm-whale the number of teeth in the lower jaw varies froni twenty to 

 twenty-five pairs ; the teeth themselves being of large size, with pointed 

 and somewhat curved crowns, upon which there is no trace of enamel. The 

 head is of enormous dimensions, measuring about one-fourth the total length 



Fig. 91. —The Spekm Whale (Physeter macracepkalus). 



of the animal, and characterised by the abrupt truncation of the enormous 

 muzzle, the S-lilce form of the blow-hole, which ia situated somewhat to the 

 left of the middle line, and the long mouth opening below, and somewhat 

 behind, the extremity of the muzzle. The sic uU behind the nostrils has an 

 enormous cavity, bounded behind by a pemi-circular wall of bone of several 

 feet in height, and containing during life the oily substance which yields, 

 when refined, the valuable spermaceti. An even more precious product of 

 this cetacean is ambergris, which, although generally found floating on the 

 surface of the ocean, is really a concretion formed in the intestines of the 

 sperm-whale. It is an amber-coloured substance, generally containing a 

 number of the horny beaks of the pquids on which sperm-whales feed. 

 Although the female is a much smaller animal, the male cachalot, as the 

 sperm-whale is often called, grows to a length of between 50 and 60 ft. In 

 the sperm-whale the two branches of the lower jaw are united in front for 

 about half their length, but in the much smaller and somewhat porpoise-hke 

 animal known as the lesser sperm-whale {Cogia hreiiceps) the union between 

 the two branches of the lower jaw is less than half the total length of the 

 j^w, and the number of lower teeth is reduced to from nine to twelve pairs. 

 This whale attains a length of about 10 ft., and differs from the cachalot 

 in carrying a large back-fin. The flippers, moreover, which in the sperm- 

 whale are remarkably small in proportion to the size of the body, are here 

 relatively longer. It is interesting to notice that foaE.il sperm-whales 

 (Physodun) have been discovered possessing a full series of enamel-capped 

 teeth in boch the upper and lower jaw. 



Nearly allied to the preceding are the bottled-nosed and beaked-whales, 

 belonging to a group distinguished by the reduction of the lower functional 

 teeth to a single pair, the others being rudimentary and con-cealed in the 

 gum. None attain a large size, and all are pelagic, subsisting almost 



