i So A BOOK OF WHALES 



p. 141.) But Neobalana offers no hints in the 

 structure of its skeleton of a toothed whale ancestry ; 

 neither does Inia or any Platanistid show a leaning, 

 however slight, towards Neobalcena. It seems, there- 

 fore, that this question is one that will have to be 

 deferred until we come to deal with the Zeuglodonts. 



As to the origin of the remaining groups of toothed 

 whales from the Platanistidae, that does not offer so 

 many difficulties. The family itself, it may be re- 

 marked, is not a very natural one. This comes from 

 the fact of its age and the consequent number of 

 extinct genera which have caused gaps. Sir William 

 Flower thus defined it in 1866 : 



" Costal cartilages not ossified. The tubercular and 

 capitular articulations of the ribs blending together 

 posteriorly. Cervical vertebrae all free. Pterygoid 

 bones thin, not conforming in their mode of arrange- 

 ment with either of the other sections. Jaws very 

 long and narrow ; both with numerous teeth having 

 compressed fangs. Symphysis of mandible very long, 

 exceeding half the length of the entire ramus. Orbit 

 very small. Lacrymal bones not distinct from the 

 jugal. Pectoral limbs large. Dorsal fin rudimentary." 



At the time that this was written but little of Pon- 

 toporia (or Stenodelphis, as it should really be called) 

 was known. But with the exception of the vertebral 

 characters, the ossified costal cartilages and the 

 presence of a back fin, it corresponds to the definition. 



* " Description of the Skeleton of Inia geoffrensis" etc., Trans. Zool. 

 Sac., vi., p. 87. 



