148 MAMMALIA. 



The Bottle-heads (Ht/peroodon, Laccp.)— 

 Have the l)oily and niuzzlo nearly similar externally to those of the Dolphins properly so ealled, hut 

 the eraninni is laterally elevated hy verlieal hony partitions: most nsnally there are found only two 

 small teeth in the foro-part nf the lower jaw, uhieh do not always appear externally; the palate is 

 studded \\\\]i small tiihercles, [ajid there is a small doi'sal tin]. 



Bat one species is known, wliidi attains a Icnstli of five-and-twenty feet, and perhaps more, [Defph. edenfi/l//.-:, 

 Schreb. ; D. bnU-Jtopf, Lacepede ; D. hidcntafi/s. Hunter; I). Hunter/, Desni. ; the Boft/e-Jioscd JMiale of Hunter]. 

 — It is taken in the British Channel and the Nurtli Se.i, and is often d(.-si;j:iiated Balci/ie a bee. 



[The r)[ODONs {Diodon, Lesson)— 

 Lrincipally differ from the preceding in having a ilatlencd forehead: their low^er jaw is much larger 

 than the upper, and eonvcx. 



There is a species in the Mediterranean (Dclph. BcsmnresHi, Risso), fifteen feet in Icnirtli ; a specimen of wliich, 

 or of another closely alhed, "as cast nn ^hore uu the coast uf Scotland (JJ. Sou-crbii, Desm. ami Blainv.) Severtil 

 others are said to lielun;,^ to this sidniivisiun.] 



The Narwhal (Monodon, Lin.) — 

 Has no teeth, properly so called ; but very long and slender-pointed tusks implanted in the inter- 

 maxillary bones, and directed in the line of the axis of the body. The form of tlu'ir budy and head 

 gi'eatly resembles that of tlie Porpoises, [and still more the Beluga, as noticed hy Prdf. Bell ; the 

 swimming paws being also remarkably small, and the dorsal tin wanting, as in the latter animal]. 



Only one sjiccies is known {^fon. mo)ioccros, Lin. ; [Nanrhaln.s inirmrrphdlns, Bonat., Lacep., Desni.] ), the tusk 

 of which, grooved spirally, and sometimes ten feet long, was formerly termed the horn of the Vtiicorn. This 

 animal possesses the g;erms of two tusks, but it is seldom that both become equally developed. Tliat on the left 

 side usually attains its full g;rowth, while the other remains permanently concealed within its socket, its dei'elope- 

 ment having been prevented by its interior cavity becoming too rapidly filled with the deposition of ivory, which 

 thus obliterates its p;elatinous core. According to the description of the Narwhal, it is scarcely more than twice 

 or three times the length of its tusk ; the skin is marbled with brown and whitish ; it has a convex muzzle, small 

 mouth, spiracle placed on the top of the head, and no dorsal tin, but merely a projecting crest the whole leu?,th of 

 its spine. The teeth are sometimes found perfectly snjooth. 



[We may here mention, at the conclusion of the Vetacca with moderate-sized heads, an extremely 

 remarkable genus, — 



Till-: LxiA, d'Orhlgny, — 



Which has the external form of the Dolphins, properly sn called, v^ilii some coarse hristlv hairs on the 

 snout; the s])iracle is ])laeed far liaekward, above the swimming-iiaws ; ibe lips arc dec[)ly cleft to 

 beneath the eye; and there is a small dorsal lin, and proportionally large anditorv aperture. 



Tlie only species known (/. Bollvii'iisis, d'Orli.) is remarkal)le for occurrin.c: thousands of miles from the ?;ea, 

 appearing: to inhabit only the remote tributaries of the Amazons, and the elevated lakes of Peru: the siu'^'-ular 

 character of possessing bristly hairs on the snout has also been observed in them when very youna;. This species 

 has lars"e swimming-paws, and thirty-four teeth on each side above and below, all of them roup:h, marked with 

 deep and interrupted furrows, and of an irre^rn'ar mammalory shape behind, which is very peculiar. A female 

 specimen measured seven feet loni^, and the males are stated to be double that size : colour variable, commonly 

 pale blue above, passing; into a roseate hue beneath. It comes more freipiontly to the surface than the marine 

 species, and is generally met with in troops of three or four individuals.] 



The rcmuining Crfacra have the hcud so very hu-a:c, as to constitute one-third or even half 

 the entire length ; but neither the cranium nor the brain ]>articipates in this disproportion, 

 which is wholly due to an enormous tlevelopcmeut of the bones of the face. 



The Cachalots {Pfn/sr/er, Lin.),- — 

 Are Cetacea with a most voluminous head, excessively enlarged, particularly in front ; in the upper jaw 

 of which there are neither teeth nor baleen {whalebone), or, if any of the former, they are small and 

 not projecting beyond the gum ; hut the lower jaw, straight, elongated, and corresponding to a groove 

 in the upper one, is armed on its two sides with a row of cylindrical or conical teetli, which enter into 

 corresponding cavities of the upper jaw when the mouth is closeil. The superior portion of their 

 enormous head consists almost entirely of large cavities, separated and covered bv cartilages, and Idle:! 

 with an od that becomes conerele on cooling, well known in commerce by the name Npornincefi a 



