62 TOOTHED WHALES AND THEIR ANCESTEY. 



coasts, and their apparently somewhat soUtary habits, 

 extremely little is known of the life-history of the beaked 

 whales, of which the skeletons are but poorly represented 

 in om' museums. At the present day very rarely seen in 

 the English seas, during the Pliocene period these whales 

 must have been extremely numerous in the North Sea, 

 since their fossilized beaks are amongst the most common 

 vertebrate fossils obtained from the crags of Suffolk and 

 Essex. The same deposits, together with others of corre- 

 sponding age on the Belgian coasts, have also yieldedremains 

 of a number of extinct whales, more or less closely allied 

 to the sperm-whale, thus indicating that the latter is the 

 last survivor of a once numerous group. The teeth of 

 many of these fossil sperm-whales differed, however, from 

 those of their living cousins in having their crown capped 

 with enamel. 



Fig. 22. — Tin- Indiau rorpoise. (From Trur, Bid/. CS. Saf. Jliiseiiin.) 



In the general presence of numerous teeth in both the 

 upper and the lower jaws, the dolphins and their allies 

 the porpoises, killers, and white-whale differ from all the 

 above-mentioned forms, and thus constitute a second family 

 — the I'elplunida. The group is a numerous one, which is 

 split up into a number of genera, some of which are by no 

 means easy to distinguish. They may, however, be roughly 

 ranged under two main divisions, in one of which the 

 muzzle is short and rounded, as in the porpoises and black- 

 fish, while in the other, as represented by the dolphins 

 (Fig. 20), it is produced into a longer or shorter beak, of 

 which the base is marked off from the main portion of the 

 head by a distinct re-entering angle. The most aberrant 

 member of the first group is the spotted Arctic narwhal, of 

 which a brief notice, accompanied by a ligure, was o-jyen 



