CETACEANS. 349 



width equalling half the diameter of the tooth ; and again, but 

 gradually, contracts to a linear fissure near the apex; Plate 87, 

 fig- 4. 



Thus the most solid and weighty part of the tooth is that 

 which is implanted in the jaw,(l) and nearest the centre of support, 

 whilst the long projecting part is kept as light as might be com- 

 patible with the uses of the tusk as a weapon of attack and defence : 

 the portion of pulp in which the process of the calcification has 

 been arrested, receives its vessels and nerves by the fissure con- 

 tinued from the basal expansion of the pulp-cavity. 



The small abortive tusk of the right side of the male Narwhal 

 (Plate 87, fig. 1) has a few slight longitudinal indentations on its basal 

 half, and is smooth on the rest of its exterior ; it is solid and closed, 

 generally by a bulbous accumulation of cement, at its base ; the apex 

 is truncated with a rough prominence from its centre : the ordinary 

 length is between eight and nine inches. The two concealed tusks 

 of the female Narwhal are of a similar size and shape.' 



Sometimes both tusks are so developed as to project from their 

 sockets in this sex ; Mr. Scoresby records such an example in his 

 Voyage to Greenland. (2) Cuvier saw at Hamburg the skull of a 

 Narwhal with two tusks projecting, which he ascribes to the male 

 sex, probably on account of their length ; and he cites two other 

 instances, one figured in the Ephemerides Naturce Curiosorum for 

 1700, p. 3.51, the other in Albers' Icones ad illustrand. Anat. Comp. 

 PL 2 and 3. 



In the cranium of the Narwhal figured by Albers, the right tusk 

 projects only six inches from the socket, is proportionally slender, and 

 is smooth. With regard to the paper in the ' Ephemerides,' or ' Miscel- 

 lanea curiosa,' (1702, p. 350), though it is entitled "De Unicornu Ma- 

 rino duplici," it gives an account, not of two projecting tusks, but of the 

 discovery by the author. Dr. Reisel, of the small concealed tooth in the 

 right maxillary bone of an ordinary male Narwhal, the tooth being eight 



(1) M. F. Cuvier appears to have been misled by ordinary analogies, in describing the 

 Narwhal's tusk as " creuse dans une grande partie de sa longeur, mais surtout dans sa partie 

 alve'olaire," Hist, de Cetaces, 8vo. 1836, p. 237. 



(2) It would be interesting to know the condition of the ovaria in such an instance. 



