A Nine-Tusked EIepha}it 275 



and increase that of the Deinothere to the same degree, we should 

 then have to enlarge it by three or four times before comparing it 

 with the tusk of the Mammoth — when we should find it vastly 

 thicker, and not much inferior to it in length ; and the thickness 

 is of more importance than the length, as indicating better the 

 size of the socket. The enormous thickening of the deflected 

 beak, or prolongation of the symphysis of the lower jaw in the 

 Deinothere, is another argument indicating unusual size. How 

 far the actual position of the tusk in this, as made out from 

 young individuals, will further corroborate our view, we must 

 leave to observers who have the opportunity of making the 

 examination to determine. The texture of the tusk of the Dein- 

 othere, so far as we can make out from a microscopic examin- 

 ation of sections in the British Museum and College of Surgeons, 

 seems to us to harmonize with this view — its density and closeness 

 being apparently greater even than of the Elephant. 



Before closing we should like to say one word on Falconer's view, 

 adopted by Mr Dawkins, that the three genera must have sprung 

 from one common ancestor, and not from one out of the three, 

 to which the reduction of their dentition into regular distinct series 

 (like three tunes played on different keys on the same instrument) 

 lends support. 



We may observe, however, that this is not a necessary corollary 

 to there being in each a distinct series of teeth. As Mr Falconer 

 says elsewhere ("British and European Fossil Mastodons," Palaeont. 

 Mem. ii., p. 17 and 18) — "Although the Mastodon of North 

 America and the Mammoth are so widely different in the form of 

 their molar teeth, that they must be ranked under distinct genera, 

 the intermediate gradations are so complete as to establish a pas- 

 sage from one into the other." And we can see no necessity 

 requiring the evolution of each form directly from the first common 

 ancestor, possessed of the proboscidean qualities ; they may be so 

 evolved directly, but there is nothing to hinder one or more of the 

 series remaining concealed and undeveloped through a long suc- 

 cession of only one of the forms ; and when the proper conditions 

 for its evolution occurred, that it should then, and only then, make 

 its appearance. Editor. 



