200 DR. J. E. GRAY ON THE CETACEANS. [May 26, 



A. Head more or less beaked ; beak of the skull as long, or longer, 

 than the brain-cavity. Bottlenoses. 



a. Pectoral Jins moderate, lanceolate, far apart on the sides of the 



chest; teeth in both the jaws permanent. Delphinina. 



1. PoNTOPORiA. Beak of skull rather compressed, high. Sym- 



physis of the lower jaw very long. Dorsal medial. 



2. Steno. Beak of the skull rather compressed, higher than broad. 



Symphysis of the lower jaw rather elongate. Dorsal medial. 



3. Delphinus. Beak of the skull rather depressed, convex above. 



Dorsal medial. 



4. Dklphinapterus. Beak of the skull rather depressed, convex 



above. Dorsal none. 



5. Lagenorhynchus. Beak of the skull depressed, expanded. 



Head shelving in front. Dorsal rather posterior. 



b. Pectoral fins small, low down, and rather close together on the 



middle of the chest; upper jaw toothless; lower jaw with few 

 teeth, sometimes deciduous. 



* Maxillary bones elevated into a crest on the sides behind; teeth 

 t%vo or four, anterior conical. Hyperodontina. 



6. Hyperodon. The crest of the maxillary bone thin and wide 



apart above. The beak of the skull descending downwards. 

 The hinder edge of the skull as high as the crest. Lower jaw 

 rather curved. Hyperodon rostratum. 



7. Lagenocetus. The crest of the maxillary bones very thick and 



close together, especially above, where they are flat-topped. 



The beak of the skull horizontal. The hinder edge of the skull 



lower than the top of the crest. Lower jaw straight. Lage- 

 nocetus latifrons. 



** Maxillary bones simple ; teeth, on the sides of the lower jaw, 

 compressed. Ziphiina. 



8. Berardus. Lower jaw gradually tapering in front. Teeth, two, 



in the front of the jaw large conical. 



9. ZiPHius. Lower jaw gradually tapering. Teeth on the sides of 



the jaw large, compressed. 



10. Delphinorhynchus. Lower jaw gradually tapering. Teeth 

 on the sides of the jaw small, conical. (Perhaps the female of 

 the former.) 



11. DioPLODON. Lower jaw broad behind, suddenly tapering in 

 front. Teeth on the sides of the jaw large, compressed. Bi- 

 oplodon densirostris. 



