36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



II. Atlas and axis coalesced. 



A. Anterior facial region, formed mostly of intermaxillary 



and maxillary, long and narrow, not or scarcely flat, 

 nearly roof-shaped ; intermaxillary in particular rela- 

 tively narrow. 

 Delphini. 



1. Crowns of teeth rough; symphysis menti long. 



Steno. 



2. Crowns of teeth smooth ; symphysis menti short. 



a. Palate without grooves. 



Prodelphinus. 

 h. Palate with a longitudinal groove on each side. 



Dclphinus. 



B. Anterior facial region, formed mostly of intermaxillary 



and maxillary, becoming relatively short, broad and 

 fiat ; intermaxillary in particular broad. 



1. Face relatively only a little shortened. 



Lagenorhynchi. 



a. Fore-face, beak, relatively long. 



a. Rostrum not wholly flattened. Dorsal 

 fin present. 

 Tursiops. 

 ft. Rostrum more flattened. Dorsal fin 

 absent. 

 Tursio [Lissodelphis']. 

 h. Fore-face relatively shorter. 

 Lagenorhynchus. 



2. Face more strongly shortened. 



a. Crowns of teeth conical, terete, pointed. 

 Globicipites. 



a. Intermaxillary not especially broad propor- 

 tionally. 

 Orca [Orcinus~\. 

 /?. Intermaxillary more or less noticeably 

 broad. 



1. Flippers not or scarcely lengthened 



and pointed. 

 Orcella. 



2. Flippers lengthened, pointed. 



a. Intermaxillary not conspicuously 

 broad anteriorly. 

 " Grampus." 



