372 DOLPHINS 



can leap right out of the water, and while in the air can turn its 

 head from side to side, a capability which has not been mentioned 

 in any other Whale. It can also stay under water for an unusually 

 long period. Captain Gray,-' who has made an accurate study of 

 this species, states that so long a period as two hours is the limit of 

 endurance ; this event occurred in the case of a harpooned Whale. 



Fam. 2. Delphinidae. — This family, which includes tlie 

 greater number of Cetacea, may thus be characterised : — Whales 

 of small to moderate size. Teeth as a rule numerous, and 

 present in the upper as well as in the lower jaw. Maxillae 

 without large crests ; the pterygoids, often meeting in the middle 

 line, enclose an air space open behind. The anterior (five to eight) 

 ribs are two headed, the posterior with tubercular head only. The 

 sternal ribs are ossified. 



The Dolphins and Porpoises, as already stated, embrace the 

 greater number of existing species of WHiales. Sir W. Flower and 

 others who have followed liim, allow nineteen genera. But as to 

 the exact number of known species there is much uncertainty. 

 That very careful observer, Mr. True, considers ^ that there are 

 fifty which demand recognition. As many as one hundred have 

 received names. The matter is one which is perhaps barely ripe 

 for decision. All the Dolphin tribe are, for Whales, smallish 

 animals. The Killer Whale, Orca, is the only genus (or species ?) 

 which usually attains to more than moderate bulk. The rather 

 mysterious Ddiphinvs coronatus, 36 feet in length, of M. de Fre- 

 minville, would seem to be a Ziphioid ; it was described as having 

 a very pointed beak, and as having the dorsal fin situated near 

 the tail ; such characters suggest a Mesoplodon. 



The genus Delpliinapterus, the Beluga or \V'hite ^Miale, con- 

 sists of but a single species, though as usual more than one 

 name has been given to supposed different species. It is char- 

 acterised as a genus by the following assemblage of structural 

 features : — It has only eight to ten teeth occupying the anterior 

 part of the jaws only. All the cervical vertebrae are free and 

 unjoined. The vertebral formula is C 7, D 11 (or 12), L 9, 

 Ca 23. The pterygoids are wide apart, though they converge 

 as if about to meet at their posterior ends. There is no dorsal 

 fin. The colour is white. 



1 Proc. Zool. Soc. 1882, pp. 722, 726. 

 Bull. U.S. Nat. Mus. No. 36, 1889, p. 7. 



