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Show 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 appears to have known no more about the paper than its title, quotes J it as an authority for the existence of a bidental cranium in the Stuttgart Museum. This error is pointed out by Dr. G. Jager in his paper. The next author who found out the fact was Tycho Tychonius at Copenhagen in 1706. His rare tract, "Monoceros piscis haud monoceros," is usually quoted as the place in 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. H o m e 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 striation 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 (Cetaces, 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 Dolphins, 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 m y 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 to left." He proceeds to argue that a proof of the correctness of this view is afforded by the bidental skulls, where the striation 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 leff^f. 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. W e know that * Museum Wormianum, 1655, p. 282 et seq. t In Ephemerides Acad. Cses. Leop. Nat. Cur. Dec. iii. Ann. vii. et viii. p. 350. X 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. || Trans. Roy. Soc. 1813, p. 126. «T Odontography, p. 350. I can find no mention of this specimen in the sale Catalogue of Brookes's Museum. P R O C ZOOL. Soc-1871, No. IV. |