206 PHILOSOPHY OF ZOOLOGY. 



round-lipped Avhale (Scoresby's " Arctic Regions," tab. 

 xiii. fig, 2.), and B. rostrata, or sharp-nosed whale (Hun- 

 ter, Phil. Trans. 1778, tab. xx.), may be regarded as 

 distinct. 



119. PiiYSALis. Finner. Without pectoral folds. 

 The longest of the whales reaching to 100 feet. The 

 most difficult to capture. 



No dorsal fin. 



120. Bal^na. Common whale. Under lip whiskered. 

 Head very large. 



Destitute of baleen. One external opening of the nos- 

 trils. 



A. Nostrils double within, being divided in the skull by 

 a bony septum. 



Teeth in the mouth. 



The following interesting remarks are made by Hun- 

 ter (and copied by Sir E. Home into his Comp. Anat. 

 i. 261-), on the dentition of whales. " The situation of 

 the teeth, when first formed, and their progress afterwards, 

 as far as I have been able to observe, is very different in 

 common from those of the quadruped. In the quadruped, 

 the teeth are formed in the jaw, almost surrounded by the 

 alveoli, or sockets, and rise in the jaw as they increase in 

 length ; the covering of the alveoli being absorbed, the al- 

 veoli afterwards rise with the teeth, covering the whole 

 fang ; but in this tribe the teeth appear to form in the 

 gum, upon the edge of the jaw, and they either sink in 

 the jaw as they lengthen, or the alveoli rise to inclose 

 them ; this last is most probable, since the depth of the 

 jaw is also increased, so that the teeth appear to sink deeper 

 and deeper in the jaw. This formation is readily disco- 

 vered in jaws not full grown; for the teeth increase in 



