THE ORDER CETACEA. 169 



ORDER IV.— AMBIDENTATE CETACEA. 

 OR THOSE HAVING TEETH IN BOTH JAWS. 



GENUS VI. 



DELPHINUS OR DOLPHINS. 



The animals of this genus are smaller than most of the 

 preceding tribes ; the largest species hardly exceeds 

 twenty-five feet. Their jaws are lengthened consider- 

 ably, but are of equal length, and are each furnished with 

 a row of conical teeth, more or less numerous in the par- 

 ticular species. The spiracles or blow-holes, after tra- 

 versing the upper jaw, unite without in a single orifice, 

 which is in the form of a crescent, and is situated at the 

 top of the head. Their eyes are placed near the angle 

 of the mouth. All the species but one are furnished 

 with a dorsal fin, which is sometimes of an enormous 

 length. They are not confined to the Arctic Ocean, 

 but in fact are found in most seas, and in the mouths 

 of most rivers. 



The exact number of species is not accurately ascer- 

 tained, but the following are most commonly known to 

 zoologists. 



