300 ON THE FOSSIL BONES OF PACHYDERMATOUS QUADRUPEDS. 



With regard to the grain (or texture) we have seen already that it 

 is precisely similar in all species ; and that in this particular, the teeth 

 of the mastodon are not distinguishable from those of the elephant. 



Hence, it only remains for us to make a comparison between their 

 curves. 



Many of the fossil tusks have a very common curve ; those for instance 

 in our Museum : those of Thiede, and most of those of Canstadt. 

 But there are many of them whose curves are much more decided 

 than is commonly observable in the tusks of living elephants. It ap- 

 proaches to a semicircle, or the half of an ellipse, divided by its smaller 

 axis. 



There are descriptions extant of four of this sort : that of Messer- 

 schmidt, in the Philosophical Transactions ; that of the Cathedral of 

 Strasbourg, according to Hermann ; that of the Church of Halle 

 in Souabe, according to Hoffmann and Beyschlag; and that of the 

 Museum of Stuttgart, according to Autenrieth and Jfeger. This 

 striking resemblance between four of the most perfect fossil tusks ex- 

 tant is well worthy of observation. The curve is still more decided in 

 the tusks of the skeleton of Mr. Adams, which form an almost perfect 

 circle or ellipse. The points of the latter terminate by again retreat- 

 ing backwards, and even by growing downwards a little, while they 

 take an external direction, so that these tusks could not have been used 

 by the animal for the usual purposes of tusks, which is to pierce or 

 raise up bodies with their points. 



Some writers have fancied that this more decided curve afforded suf- 

 ficient grounds for supposing a distinct species ; but we may be satis- 

 fied with attributing it to the length of the particular tusks in which it 

 has been observed, and to the age of the individual animals. 



As part of the tusk never changes after it has been once formed, if 

 this part is not perfectly straight, every additional increase of length 

 will be an increase in the number of the degrees of the circle that it 

 describes. Thus it is that the incisive teeth of rabbits, where the cor- 

 responding teeth are broken, curl up in a spiral form. 



Nevertheless, it is worthy of observation, that an African tusk pre- 

 served in our Miiseum, although six feet in length, is not by any 

 means so much curved as the four I have just cited. 



Moreover, we may remark that in the case of very old living 

 elephants, the tusks grow blunt at the point in proportion to their pro- 

 longation from the root ; this is visible in the old skull of plate 18. 

 But perhaps the fossil elephant had not so much occasion for the use 

 of his tusks as the elephant of our times. 



There are also some fossil tusks twisted into the shape of worm- 

 screws, as is sometimes the case with those of living animals. Pallas 

 cites one belonging to the Museum of Petersbourg*. There is another, 

 though not so much twisted, in the Museum of Stockholm, a drawing 

 of which has been forwarded to me by the kindness of M. Quensel. 

 Thus it is clear that tusks cannot be made use of to establish any 



* Nov. Com., p]. xiii, p. 473. 



