136 DiT. 1. VERTEBRATE ANIMALS.— MAMMALIA. Class 1. 



The Bottle-heads {Ilyperoodon, Lacep.) — 



Have the body and muzzle nearly similar externally to those of the Dolphins properly so called, but 

 the cranium is laterally elevated by vertical bony partitions : most usually there are found only two 

 small teeth in the fore-part of the lower jaw, which do not always appear externally ; the palate is 

 studded with small tubercles, [and there is a small dorsal fin]. 



But one species is known, wliicli attains a lenp:tli of five-and-twenty feet, and perhaps more, [Delph. cdentuhis, 

 Schreb. ; D. btilshopf, Lacepede ; D. bidentatus. Hunter ; D. Hinifen, Desm. ; the Bottle-nosed Whale of Hunter]. 

 — It is taken in the British Channel and the North Sea, and is often desig'nated Baleine a bee. 



[The Diodons {Diodon, Lesson)— 



Principally differ from the preceding in having a flattened forehead : their lower jaw is much larger 



than the upper, and convex. 



Tliore is a species in the Mediterranean {Delpli. Desmarestii, Risso), fifteen feet in length ; a specimen of which, 

 or of another closely allied, was cast on shore on the coast of Scotland (Z). Sotcerbii, Desm. and Blainv.) Severa' 

 others are said to belong to this subdivision.] 



The Narwhal (Monodon, Lin.) — 



lias 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 their body and head 

 greatly resembles that of the Porpoises, [and still more the Beluga, as noticed by Prof. Bell ; the 

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



Only one species is known (3Ton. monoccros, Lin. ; [Narivhalus microeephalus, Bonat., Lacep., Desm.] ), the tu.sk 

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

 animal possesses the germs of two tusks, but it is seldom that both become equally developed. That on the left 

 side usually attains its full growth, while the other remains permanently concealed within its socket, its developo- 

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

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

 or three times the length of its tu.sk ; the .skin is marbled with brown and whiti.sh ; it has a convex muzzle, small 

 mouth, spiracle placed on the top of the head, and no dorsal fin, but merely a projecting crest the whole length of 

 its spine. The teeth are sometimes found perfectly smooth. 



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

 remarkable genus, — 



The Inia, d'Orbigny, — 



^A'hich has the external form of the Dolphins, properly so called, with some coarse bristly hairs on the 

 snout : the spiracle is i)laced far backward, above the swimming-p.aws ; the lips are deeply cleft to 

 beneath the eye ; and there is a small dorsal fin, and proportionally large auditory aperture. 



The only species known (/. BoUviensis, d'Orb.) is remarkable for occurring thousands of miles from the sea, 

 appearing to inhabit only the remote tributaries of the Amazons, and the elevated lakes of Peru: the singular 

 character of possessing bristly hairs on the snout hiis also been observed in them when very young. This species 

 has large swimming-paws, and thirty-four teeth on each side above and below, all of them rough, marked with 

 deep and interrupted furrows, and of an irregular mammalory shape behind, which is very peculiar. A fcuiule 

 specimen measured seven feet long, 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 frequently to the surface than the marine 

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



The remaining Cetacea have the hcnd so very large, as to constitute one-third or even half 

 the entire length ; but neither tlie cranium nor the brain participates in this disproportion, 

 wliieli is wholly due to an enormous developement of the bones of the face. 



The Cachalots {Physeter, Lin.), — 

 Are Celacen with a most voluminous bead, excessively enlarged, particularly in front ; in the upper jaw 

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

 )iot projecting beyond the gum ; but 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 teeth, which enter into 

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

 enormous head consists almost entirely of large cavities, separated and covered by cartilages, and filled 

 with an oil that liecomes concrete on cooling, well known in commerce by the name spermaceti, a 



