112 ME. W. H. FLOWEE ON THE OSTEOLOGY OF 



these may also be added Platanista and Inia. Here, then, is a character derived from a 

 part of the organization apparently less liable to adaptive modification than the teeth or 

 fins, which may be taken as the basis of a primary division. It must now be seen whe- 

 ther the remaining essential structural modifications are in accordance with it. Still 

 confining our attention to the axial skeleton, there are certain tolerably obvious pecu- 

 liarities about the vertebral column, more especially in the thoracic region, that will 

 afl^ord considerable assistance. As before indicated (p. 98), a peculiar mode of attach- 

 ment of the ribs to the vertebrae is constantly found associated with the sterno-costal 

 bones. The genera thus characterized may therefore be separated at once as a distinct 

 natural gi-oup. They have also several minor characters in common, which will be 

 pointed out presently. 



Should the whole of the genera with cartilaginous sternal ribs be united into a single 

 group, equivalent to that just marked off? I am inclined to think that they should 

 not. To revert to the same point of structure just mentioned, it was shown before that 

 Physeter and Hyperoodon agree in a very peculiar condition of thoracic vertebrae and 

 rib-attachments. Whether Kogia and the Ziphioids conform with their nearest allies 

 in this respect I am not at present able to say; but we may assume with tolerable 

 certainty that they do. But here, as well as in many more trivial characters, including 

 the teeth and pectoral limbs, Inia and Platanista differ^and differ, as it appears to me, 

 more than any of the true Dolphins do, inter se. I would therefore raise the Cacha- 

 lots and Ziphioids on the one hand, and Platanista and Inia on the. other, to the rank 

 of primary divisions of the Toothed Whales. With the latter it is in the highest degree 

 probable that the genus Pontoporia should be associated. This group is not so com- 

 pact and easily defined by positive characters as the other two, between which it 

 naturally stands. The two genera whose structure is most completely known vary 

 widely from each other, one diverging towards the Physeteridce, the other towards the 

 Delphinidse, yet distinctly marked off from either. The validity of the group as a 

 natural one will be greatly strengthened if the skeleton of Pontopona should be found 

 to possess the characters common to Platanista and Inia*. It would be interesting, 

 moreover, if it should be discovered that this Dolphin is, like the members of the other 

 two genera, habitually fiuviatilef. 



* Dr. Gray in the " Zoology of the Voyage of the Erehus and Terror " placed Inia and Pontoporia in one 

 section at the end of the family Dcl])hiuida;, following immediately upon Platanista. In his recently published 

 Catalogue, Platanista constitutes the fourth famQy (Platanistidse) of the Cetacea, following the Catodoiitidie ; 

 Inia forms a separate (the fifth) family, IniidEe ; and Pontoporia commences the sixth family (Delphinid^), 

 comprising all the remaining Dolphins except the GlobiocephalidiE and the Ziphiida;. 



Ger^'ais (Hist. Xat. des ilammiferes, 1855) unites Platttnista, Inia, and Stenodelphis {Pontoporia) to form 

 one of the five tribes (Platanistins, Delphmins, Orcins, Monodontins, and Phocenins) into which the family 

 DelphinkUs is divided. The primary divisions of the order or families are i—Physeterides, Ziphiides, Ddphinidh, 

 and BaUnides. 



t It is to be hoped that Dr. Burmcister may be able to obtain information on this point. I should mention 



