CETACEA. Ill 



DELPHINUS, Cuvier. 



The Dolphins, properly so called, have a convex forehead, and the muzzle 

 forming a kind of rostrum, or snout, in front of the head, more slender than 

 the rest 



PHOC.SNA, Cuvier. 

 The Porpoise* has no rostrum, but a short and uniformly convex muzzle. 



Monodon, Linnaeus. 



The Narwhals have no teeth, properly speaking, but mere long, straight 

 and pointed tusks, implanted in the intermaxillary bone, and 

 directed in the line of the axis of the body. The form of their body 

 and that of their head greatly resemble that of the porpoises. One 

 species only is well known, the 



M. monoceros, Lin. (The Narwhal.) The tusk of this animal, 

 which is spirally furrowed and sometimes ten feet in length, was for a 

 long time called the horn of the unicorn. It has, it is true, the germs 

 of two tusks, but it is very seldom that both become equally developed. 



That of the left side usually attains its full growth, while the other always 



remains hidden in its alveolus. 



The other cetacea have the head so large as to constitute one third or one 



half of the length of the whole body ; but neither the cranium nor the brain 



participates in this disproportion, which is altogether owing to an enormous 



development of the bones of the face. 



PHYSETER, Linnteus. 



The Cachalots f are Cetacea with a very voluminous head, excessively 

 enlarged, particularly in front, in whose upper jaw there is neither whalebone 

 nor tooth, or if any, very small,' and not projecting ; the lower jaw, narrow, 

 elongated, and corresponding to a furrow in the upper one, is armed on each 

 side with a range of cylindrical or conical teeth, which, when the mouth is 

 closed, enter into corresponding cavities in the upper jaw. The superior 

 portion of their enormous head consists almost entirely of large cavities, 

 separated and covered by cartilages, and filled with an oil which becomes fixed 

 as it cools, well known in commerce by the name of spermaceti, a substance 

 for which they are principally sought ; the body not having much fat, and 

 consequently yielding but little oil These cavities, however, are very distinct 

 from the true cranium, which is rather small, is placed under their posterior 

 portion, and contains the brain as usual. 



* Porpoises from porcus piscis, hog-fish. 



f Physeter, as well as physalus, signifies blower. Cachalot is the name used by the 

 Bisctiyans ; from cachau, which in the Cantabrian dialect means tooth. 



