WHALES AND PORPOISES 39 



the island of Skye. But in a more remote period in the history 

 of this species, sperm whales closely allied to the existing form 

 were common in English seas, and their remains are preserved in 

 East Anglian rocks of the Pliocene period. 



SUB-FAMILY : ZIPHIIN^. ZIPHIOID OR BEAKED WHALES 



A small Physeteroid or sperm whale (represented by the 

 genus Kogia found in the Antarctic seas, and not much larger in 

 size than a porpoise) forms some link between the huge sperm 

 whale and the outwardly very dissimilar remaining members of 

 the Physeterid<, who are grouped together as a sub-family, 

 Ziphiintf. In the Ziphiines there are no functional teeth 1 what- 

 ever in the upper jaw, and in the lower jaw the teeth are reduced 

 to one pair, or more rarely to two pairs. These scanty teeth 

 sometimes become very large in the males, and are perhaps used 

 for fighting in some species. A marked feature in the Ziphioids 

 is the extraordinary development of crests of bone behind the 

 ear or in front of the nasal openings at the top of the skull. 

 These bony crests support great bulging foreheads of fatty tissue 

 containing spermaceti. They are even more exaggerated in the 

 male than in the female. The upper jaw is prolonged into a 

 long and narrow beak, usually not much, if at all, under-hung by 

 the lower jaw. In nearly all the Ziphioids there are marked 

 longitudinal grooves on each side of the throat. All possess a 

 small back fin. The blow-hole is single, shaped like a crescent, 

 and usually in the middle of the huge bulging forehead of fatty 

 tissue. 



The stomach of the Ziphioid whales is a peculiar feature, and 

 contains a great many compartments, sometimes as many as 

 fourteen. All the Ziphioid whales, being, for masticating and 

 snatching purposes, practically toothless, live entirely on cuttle- 

 fish and small, soft-shelled sea animals. Indeed, it is no doubt 

 this diet, so much affected by many groups and species of 

 whales, which is gradually causing the disuse of the functional 

 teeth. All these Ziphioids with whom man has come into 



1 That is to say, the teeth practically never pierce the gums. 



