inches in length, and exposed by the laying open of the narrow socket
(‘ rima’), in which it was lodged. Two very accurate views of this abortive
tusk are given in the figures 23 and 24 of the Plate which illustrates
the paper, and the Author conjectures that it may serve to supply the
place of the large left tusk should this he either broken away by violence,
or shed naturally in process of time. The normal tusk in the skull of the
Narwhal, ‘ Cete Narhual’ the subject of his observation, was inserted
fourteen inches deep, and projected nearly four feet from the socket,
but its extremity had been broken off. It is figured in the Plate, together
with two views of the skull from which the tusks are removed,
the fissure, or alveolus of the abortive tusk being shown in Fig. 21.
The plate hears no number, but is marked p. 35. I doubt whether
Cuvier had ever read this paper : it has the priority of Tichonius’
often cited Dissertation “ Monoceros piscis haud monoceros,” by four
years, having been printed in 1702.
The skull of a Narwhal, with two long exserted tusks, formed
part of the collection of the late Joshua Brookes ; in this specimen
the alveolus of the right tusk appeared to have been artificially
enlarged, and the tusk was unquestionably cemented in its place ; but
the circumstance which most militated against its authenticity was
the direction of the spiral lines which corresponded with, instead of
opposing those of the left tusk.
With regard to the conjectured ulterior use of the concealed tusk
in the male as a substitute in the event of the loss of the large tusk
—a conjecture more than once repeated since first proposed by Reisel,
■—the solidity of the concealed tusk and its distorted and generally
closed base evince that the term of its growth has expired.
142. Delphinidoe. In the Delphinus griseus the dentition of the
upper jaw is transitory as in the Hyperoodon, but at least six
pairs of teeth rise above the gum, and acquire a full development
at the fore-part of the lower jaw : the crowns of these teeth soon
become obtuse ; and even their duration is limited, for the specimen
described by M. F. Cuvier(l) had but two teeth on each side of the
lower jaw. A Dolphin, perhaps an aged individual of this species,
has lately been described with the dentition reduced to two teeth
(1) Dents de Mammifères, p. 243. It was eleven feet in length, and captured at Brest.
in the lower jaw(l). The permanent or mature dentition of the
Beluga (Delphinus leucas, Pall.) is more normal though scanty, nine
teeth being retained on each side of the upper jaw, and eight in each
ramus of the lower jaw; they present the form of straight, subcompressed,
obtuse cones. The Delphinus globiceps, which has jfzjt = 52
strong, conical and pointed teeth in the vigour of its age, begins
soon after to lose them, and in aged individuals none remain in
the upper jaw, and not more than eight or ten are preserved in
the lower jaw; those at the anterior part of the jaws last longest
and their summits are received in cavities in the upper jaw, or
the gum covering it, when the mouth is shut.
The most formidable dentition is that of the predaceous Grampus
(Phoccena Orca) whose laniariform teeth are as large in proportion
to the length of the jaws, as in the Crocodile ; they are in
number gEg — 50, all fixed in deep and distinct sockets, separated
by interspaces which admit of the close interlocking of the upper
and lowrer teeth when the mouth is closed. The longest and largest
teeth are at the middle of the series, and they gradually decrease
in size as they approach the ends, especially the posterior one;
the shortness of the anterior teeth is in great part due to the
wearing down of the sharp summits, which are best preserved
in the small posterior teeth ; the position of the bruising and
piercing teeth being the reverse of what commonly obtains. An
analogy to this circumstance in the dentition of the great predatory
Dolphin, is however, manifested by the typical carnivorous quadrupeds
in wThich the incisors are shaped more like grinders than
the back teeth.
In the great or Bottle-nose Dolphin (Delphinus tursio) the
teeth are fewer and larger in proportion to its size than in the
common Delphinus delphis; but proportionally less developed and
more numerous than in the Grampus, the dental formula being
ftg = go with a variation of three or four more or less in each
jaw; the teeth are conical, sub-obtuse, the posterior ones smaller
and sharpest. In the common Dolphin the number of teeth amount
to 190, arranged in equal numbers above and below. They have
(1) Proceedings of the Acad, of Philadelphia, 1842, p. 12'J.