1871.] MR. J. W. CLARK ON THE NARWHAL. 49 



of observing the tooth in situ. He recognized the animal to which 

 it belonged as a Cetacean, and gives a tolerably accurate description 

 and figure*. 



The existence of the second tooth was unsuspected till Solomon 

 Reisel discovered it in a skull at Stuttgart. His paper " De uni- 

 cornu marino duplici," dated Dec. 23, 1700, contains the first 

 announcement of the fact, with a tolerable figure f. Cuvier, who ap- 

 pears to have known no more about the paper than its title, quotes^; 

 it as an authority for the existence of a bidental cranium in the 

 Stuttgart Museum. This error is pointed out by Dr. G. Jiiger in 

 his paper. The next author who found out the fact was Tycho 

 Tychonius at Copenhagen in 1/06. His rare tract, " Monoceros 

 piscis haud monoceros," is usually quoted as the place iu which the 

 fact is first stated §. Reisel considered that the second tooth was kept 

 in reserve, as it were, to replace the fully-grown one in case it should 

 be destroyed by an accident. Crantz knew that the second tooth 

 existed, and held the same views as Reisel respecting it (Greenland, 

 i. 105). Subsequently Sir E. Home went into the question once 

 more, and published some good figures of male and female skulls 

 with the tusks in situ, from specimens in the Hunterian collection [|. 



The striatum of the exserted tusk is always from right to left. I 

 am not aware that this had ever been denied till Prof. Lilljeborg 

 advanced his theory, though Lacepede speaks doubtfully on the 

 subject (Cetace's, p. 146). Reinhardt remarks, " It seems to me 

 that the spiral twisting of the tooth must evidently be considered as 

 an effect of the same cause which produces the general asymmetry 

 in the cranium of the Narwhal, as well as in those of all other Dol- 

 phins, the whole skull being twisted from the right towards the left 

 side. That a tooth developed on the right side should be twisted to 

 the left is, in my opinion, so far from being any thing unnatural, 

 that it would, on the contrary, be quite incomprehensible if the tusk 

 remained uninfluenced by that power which causes the whole skull 

 to be twisted from right fo left." He proceeds to argue that a proof 

 of the correctness of this view is afforded by the bidental skulls, 

 where the striatum of the right tusk is the same as that of the left 

 (figs. 1,2). It is curious to remark that Owen's chief reason for 

 rejecting a bidental skull in Brookes's Museum was the fact that the 

 spiral lines on the right tusk corresponded with, instead of opposing, 

 those on the left^T. 



Reinhardt proceeds as follows : — " There is only one supposition 

 that would make me feel inclined to believe that the tusk of a 

 Narwhal could be twisted from the left to the right. We know that 



* Museum Wormianum, 1655, p. 282 et seq. 



t In Ephernerides Acad. Cjcs. Leop. Nat. Cur. Dec. iii. Ann. vii. et viii. v>. 350 



\ Oss. Foss. v. p. 321. 



§ Egede seems to have been aware of the existence of the second tooth. He 

 probably learnt it during his residence in Greenland. His work was published 

 in 1741. Comp. Egede's 'Greenland,' English transl. Lond. 1818, p. 77. 



II Trans. Eoy. Soc. 1813, p. 126. 



*f Odontography, p. 350. I can find no mention of this specimen in the sale 

 Catalogue of Brookes's Museum. 



Proc. Zool. Soc. — 18/1, No. IV. 



