CETACEA. 119 



Phocjena, Cuv. 

 The Porpoisesi,!) have no rostrum, but a short and uniformly convex 

 muzzle. 



MoNODON, Lin. 

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

 and pointed tusks, implanted in the intermaxillary bone, and directed in 

 tlie hne 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, L. (Tlie 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 participate in this disproportion, which is 

 altogether owing to an enormous development of the bones of the 

 face. 



Physeter, Lin. 

 The Cachahts(2) are Cetacea with a very voluminous head, excessively en- 

 larged, 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 cori'esponding cavities in the upper jaw. The supe- 

 rior 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, liowever, are 

 very distinct from the true cranium, which is rather small, is placed under 

 their posterior portion, and contains the brain as usual. 



The odorous substance, named ambergris, appears to be a concretion 



(1) Poi-poises from jDorcusjoisas, hog-fish. 



(2) PA?/sefer, as well as pAysa/us, signifies i/oioer. Cachalot is the name 

 used by the Biscayans; from cachau, which in the Cantabrian dialect means 

 tooth. 



