THE ORDER CETACEA. 147 



ORDER III.— SUBDENTATE CETACEA, 

 OR, THOSE HAVING TEETH ONLY IN THE LOWER JAW 



GENUS V. 



THE PHYSETERS, 

 THE CACHALOTS, OR SPERMACETI WHALES. 



The animals of this tribe are remarkable for the size of 

 their head, which in some species is equal to the half 

 and in others to a third of the whole animal. The upper 

 jaw is excessively broad and deep, and has usually a few 

 indistinct teeth almost covered with the gum ; the lower 

 jaw is long and narrow, enters into a fissure in the upper 

 jaw, and is furnished on each side with a row of thick 

 conical teeth, more or less obtuse. The blow-holes ap- 

 proach each other within the skull towards the anterior 

 part of the snout, where they terminate in a common 

 external opening. Below the snout is the principal 

 cavity which contains the spermaceti, and it is chiefly 

 from these animals that ambergrease is obtained. Some 

 of them have a dorsal fin, others a callous protuberance 

 on the back. There are several species. The oil ob- 

 tained from these whales is denominated " Sperma-Ceti 

 Oil" and is deemed to be superior to that derived from 

 the preceding species. 



l 2 



