I9081 TRUE— ON THE CLASSIFICATION OF THE CETACEA. 389 



Iniinas 



Belugfinse 



Inia. 



Pontistes. 



Stcnodelphis. 



Beluga. 

 Monodon. 



The partial breaking up of the currently-accepted families Plat- 

 anistidse and Delphinid?e here shown is quite radical. Usually Plata- 

 nista, Inia and Stcnodelphis (the so-called " river-dolphins ") are 

 united to form the family Platanistidse, but Professor Abel leaves 

 only the genus Platanista in that family. The limits of the family 

 have always been uncertain, and Sir Wm. Flower, though accept- 

 ing it provisionally in its usual form, remarked: "There are three 

 distinct genera, which might almost be made the types of families, 

 but it is probably more convenient to keep them together, only regard- 

 ing them as representing three subfamilies."^*^ 



Stcnodelphis, although having separate cervicals and broad lum- 

 bar diapophyses like Inia, has involuted pterygoids, ossified sternal 

 ribs, and the articulations of the ordinary ribs with the vertebrse as 

 in Delphinidse. Associated with it is the fossil genus Pontistes of 

 South America, which resembles Stcnodelphis very closely, but is 

 larger. The prenarial region in these genera, as well as the form 

 and position of the nasals and the form of the zygomatic processes, 

 recall Phoccena and also Inia, but I have been unable to satisfy my- 

 self of the importance of these resemblances. 



The most radical feature of Professor Abel's classification is 

 the removal of the white whale and narwhal (Dclphinaptcnis and 

 Monodon) from the Delphinidse to the Iniidas, although it is true 

 that these forms had previously been considered as constituting a 

 separate subfamily of the Delphinidse by Gill, Flower and myself. 

 They agree with Inia in having no dorsal fin, a broad pectoral, and 

 separate cervical vertebrae, and the diapophyses of the lumbars are 

 somewhat expanded. On the other hand, the sternal ribs are ossi- 

 fied, the sternum is shaped as in other Delphinidse, the ribs articu- 

 late with the vertebrse in the same manner as in that family, and 

 the enamel of the teeth is smooth. This combination of charac- 



^° Flower and Lydekker, " Mammals Living and Extinct," 1891, p. 258. 



