A Nine-Tusked Elephant 271 



Mastodon. But here an interesting question arises — What incisor, 

 in point of order, do these tusks represent ? Heretofore, 

 we have been accustomed to consider the tusks of the Deino- 

 therium as representing the same incisors (in their order) as 

 those of the Mastodon — that, in fact, the lower jaw of the 

 Deinotherium was merely that of the Mastodon bent down, 

 and that these, as well as the tusk of the elephant and 

 Mastodon in the upper jaw, represented one and the same 

 incisor (in order) in all. We do not know that there is any 

 authority for the belief, or that any one has made it actually the 



Fig. 6. 



subject of investigation ; indeed, there have hitherto been no 

 termini habiles from which such an investigation could proceed, 

 but Mr Dawkins informs us that he considers that the current 

 belief among palaeontologists is, that the tusks in all three represent 

 the same incisor, based, so far as can be made out, on a theory that 

 if any incisors of any beast be undeveloped, they jnust be either 

 I. 2 or I. 3 ; but, as he admits, adhuc sub judice lis est. Up to 

 this time the theory could not h»e called more than a conjectural 

 hypothesis. The new information contributed by this elephant, 

 however, would seem to sweep this theory clean away, and teach us 



that all the incisors are equally liable to non-development, and that 

 in the same family now one, now another, and again a third, may in 

 their turn be the subject of e.xcessive development at the expense of 

 the other. 



Taking six incisors as the tjq^ical number in all herbivorous 

 animals — that is, three on each side in each jaw, under the theory 

 alluded to by Mr Dawkins — the incisor which should be most de- 

 veloped should always be the first, and if two only are present, 

 then the two first ; but we should read ordinary facts differently. 

 In mammals generally, we think {e.g., camivora, cattle, deer, &c.), 



