1863.] DR, J. E. GRAY ON THE CETACEANS. 199 



b. Borsal Jin distinct ; belly plaited ; baleen short and broad ; 

 vertebra of neck more or less free ; pectoral lanceolate. 



2. Megaptera. Pectoral fin elongate. Dorsal fia low, truncate. 



3. Bal^noptera. Pectoral fin moderate. Dorsal fin falcate, 



two-thirds the entire length from nose. Vertebrae 46 or 48. 



4. Physalus. Pectoral fin moderate. Dorsal fin falcate, three- 



fourths the entire length from nose. Vertebrae 54-64. 



Fam. 2. CATODONTIDiE. 



Head large, subcylindrical, blunt. Lower jaw narrow. Teeth 

 large, in the lower jaw only, fitting into pits in the gums of the 

 upper one. Nostrils separate, one often abortive. The hinder edge 

 of the maxillary elevated, forming a concavity on the forehead of 

 the skull. Pectoral broad, truncated. 



* Head subcylindrical, truncated ; nostril in front of the truncated 

 head ; dorsal hump rounded. 



1. Catodon. Head very large, one-third of the entire length of 



the animal. 



** Head depressed, rounded in front ; nostrils in the forehead; 

 dorsal fn falcate. 



2. Physeter. Head very large, one-third of the entire length of 



the animal, rounded, convex above. Teeth conical, compressed. 

 Skull elongate ? 



3. }LoGiA = Euphyseter,Wa[\. Head short, very broad. Forehead 



convex. Teeth conical, cylindrical. Skull very short and broad. 



Fam. 3. Platanistid^. 



Head small, long-beaked, beak compressed. Teeth in both jaws, 

 at first cylindrical, becoming compressed. Blowers linear, parallel, 

 over the eyes. The sides of the maxilla elevated, forming a vaulted 

 cavity over the forehead. Pectoral broad, truncated. 



I. Platan I ST A. 



II. Nostrils united into a single transverse or crescent-shaped blower. 



Head moderate, more or less beaked. Teeth in both jaws, often 

 deciduous. The pectoral fin lanceolate, tapering, 



Fam. 4. Iniad^. 



The head beaked, beak hairy. Teeth rugulose, crown with an 

 internal process. Back without any fin, keeled behind. Pectoral 

 fin large. 



1. Inia. 



Fam. 5. Delphinid.^. 



Head more or less beaked, smooth. Teeth simple, cylindrical, 

 conical, smooth. Back rounded. Dorsal fin distinct, falcate, rarely 

 wanting. 



