Dr. J. E. Gray on the Arrangement of the Cetaceans. 173 
A. Head more or less beaked ; beak of the skull as long as, or longer 
than, the brain-cavity. Bottlenoses. 
a. Pectoral fins moderate, lanceolate, far apart on the sides of the 
chest ; teeth in both the jaws permanent. Delphinina. 
1. Ponrororta. Beak of the skull rather compressed, high. Sym- 
physis of the lower jaw very long. Dorsal medial. 
2, Sreno. Beak of the skull rather compressed, higher than broad. 
Symphysis_ of the lower jaw rather elongate. Dorsal medial. 
3. Detrurinus. Beak of the skull rather depressed, convex above. 
Dorsal medial. 
4, Detpuinaprervs. Beak of the skull rather depressed, convex 
above. Dorsal none. 
5, Lacenoruyncuus. 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. 
* Mazillary bones elevated into a crest on the sides behind; teeth 
two or four, anterior conical. yperodontina. 
6. Hyperopon. The crests of. the maxillary bones 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. Lacenocetus. The crests 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. 
** Mazillary bones simple ; teeth, on the sides of the lower jaw, 
compressed. Ziphiina. 
8. Berarpus. Lower jaw gradually tapering in front. Teeth, two, 
in the front of the jaw, large, conical. 
9. Ziewivs. Lower jaw gradually tapering. Teeth on the sides of 
the jaw, large, compressed. 
10. DeLeHinoruyNncHus. Lower jaw gradually tapering. Teeth 
on the sides of the jaw, small, conical. (Perhaps the female of 
the former.) 
11. DiopLopon. Lower jaw broad behind, suddenly tapering in 
front. Teeth on the sides of the jaw, large, compressed. Di- 
oplodon densirostris. 
