MAMMALIA. 
148 
The Bottle-heaps {Hyperoodon, Lacep.) — 
Have the body and muzzle nearly similar externally to those of the Dolphins properly so called, hut i 
the cranium is laterally elevated hy 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, which attains a length of five-and-twenty feet, and perhaps more, {DelpJi. edentulus, ; 
Schreb. ; D. bulshopf, Lacepede; D. bidentatus, Hunter; D. Hunteri, Desm, ; t\ie Bottle-nosed Whale of Hunter]. 
—It is taken in the British Channel and the North Sea, and is often designated Baleine d 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. 
There is a species in the Mediterranean {Delph. Besmarestii, Risso), fifteen feet in length ; a specimen of which, 
or of another closely allied, was cast on shore on the coast of Scotland (D. Sowerbii, Desm. and Blainv.) Several 
others are said to belong to this subdivision.] 
The Narwhal {Monodon, Lin.) — 
Has no teeth, properly so called ; hut very long and slender-pointed tusks implanted in the inter- 
maxillary hones, 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. Beil ; the 
swimming paws being also remarkably small, and the dorsal fin w'anting, as in the latter animal]. 
Only one species is known {Mon. monoceros, Lin. ; [Narwlmlus microcephalus, Bonat., Lacep., Desm.] ), the tusk 
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 i 
side usually attains its full growth, while the other remains permanently concealed within its socket, its develope- 
ment having been prevented by its interior cavity becoming too rapidly filled 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 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 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, — 
Which has the external form of the Dolphins, properly so called, with some coarse bristly hairs on the I 
snout : the spiracle is placed far backward, above the swimming-paws ; 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 (J. Boliviensis, 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 has 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 female 
specimen measured seven feet long, and the males are stated to be double that size : colour variable, commonly i 
pale blue above, passing into a roseate hue beneath. It comes more frequently to the surface than the marine | a 
species, and is generally met with in troops of three or four individuals.] 
The remaining Cetacea have the head so very large, as to constitute one-third or even half ^ \ 
the entire length ; hut neither the cranium nor the brain participates in this disproportion, ^ ^ 
wdiich is wholly due to an enormous developement of the bones of the face. | 
The Cachalots {Physeter, Lin.), — |i 
Are Cetacea with a most voluminous head, excessively enlarged, particularly in front ; in the upper jaw 1 1 
of which there are neither teeth nor baleen {whalebone), or, if any of the former, they are small, and | 
not projecting beyond the gum ; but the lower jaw, straight, elongated, and corresponding to a groove I 
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 becomes concrete on cooling, well known in commerce by the name spermaceti^ a 
