SQUALODONTS AND ZEUGLODONTS. 63 



Chinese White Another representative of this group is the Chinese white dolphin 



Dolphin. ($ sinensis), from Quemoy Island, in the harbour of Amoy, and the 

 Foochow and Canton rivers. It is said to be characterised by its general milk- 

 white colour, pinkish fins, and black eyes. 



Camerun The most interesting member of this group is, however, the 



Dolphin. recently described Camerun dolphin (S. teuzsi) from the estuaries and 



THE PALE RIVER-DOLPHIN. 



(From True, Bulletin of the U.S. National Museum, 1889.) 



rivers of the Camerun district of Western Africa, which is reported to be of 

 herbivorous habit. If this alleged habit should be confirmed, this dolphin will 

 differ not only from all the other members of the family to which it belongs, but 

 likewise from all other living Cetaceans. 



SQUALODONTS AND ZEUGLODONTS. 

 Families SQUALODONTID^l and ZEUGLODONTID^E. 



In addition to numerous extinct representatives of the existing Cetacean 

 families, to some of which reference has been made above, there are two extinct 

 groups which cannot be included in either of the existing families ; one of these 

 differing very much indeed from all modern Cetaceans. 



The name of squalodonts (Venus Squalodoii) is applied to the 

 Squalodonts. f r 



members of the first of these two groups on account of the somewhat 



shark-like structure of their cheek-teeth. In the general characters of their skulls 

 these Cetaceans approximate to the modern dolphins, from which they are, however, 

 at once distinguished by the teeth being of different characters in different parts 

 of the jaws, as in ordinary mammals. They have a total of fifteen teeth on each 

 side of both the upper and lower jaws. Of these the first four are of simple 

 structure, and correspond to the incisors and canines of other mammals ; the next 

 four, which are also comparatively simple, appear to represent the premolars ; while 

 the last seven have two roots, and laterally-compressed triangular crowns, with 

 sharp cutting edges, upon which there are a number of cusps arranged in a saw- 

 like manner. The squalodonts, which are found in Miocene and Pliocene forma- 

 tions, both in the Old and New World, clearly form one step between modern 

 Cetaceans and ordinary mammals. And, so far as the structure of their teeth can 

 be relied upon, they appear to suggest a kinship between Cetaceans and Carnivores. 



