A Nine-Tusked Elephant 273 



it cannot be the third. It must either be the second or the first. 

 It must either be homologous with that of the Elephant, or else be 

 incisor No. i. Now, in estimating the probabilities for and against 

 this, we do find some slight difterences between the tusk of the 

 Mastodon and Elephant. In dealing with the tusks of the Mas- 

 todon we are here assuming that both those in the upper and 

 under jaw represent the same incisor. It is only an assumption, but 

 the laws of symmetry will probably bear us out. We are obliged to 

 assume it, or we should not be able to compare the two, for it is 

 obvious, that if the upper and under Mastodon tusks do not represent 

 the same tooth, we have nothing to compare with the tusks of the 

 elephant. We might compare the upper tusks of the Mastodon 

 with them, but if they are not the same as the under tusks the 

 argument would not affect the latter. Assuming them to be the 

 same, the differences between them and those of the Elephant's 

 are, first, that they are somewhat differently shaped ; they project 

 nearly straight forward, being only slightly deflected from the line 

 of the molars. This at least, so far as it goes, is not an argument 

 for identity of tooth, but rather the reverse. Next, they are pro- 

 portionally smaller than the tusks of the Elephant and Mammoth. 

 If we are right in regarding the inner incisors as the smallest, this 

 points to their representing an incisor within that of the Elephant. 

 Their texture may furnish another plea. 



Mr Baines mentions one commercial fact relating to the teeth 

 of the Hippopotamus, which may or may not have some bearing on 

 this point. It appears that the canine teeth in the lower jaw of 

 the Hippopotamus are of finer and better texture than the projecting 

 incisors. Mr Baines says that the latter do not sell for ivory, while 

 the canines do. We have above said that there seems no reason 

 in such a question as this for putting the canines in a different 

 category from the incisors. But although we were to do so, it 

 would not affect our argument, which is, that if the dentine of the 

 Mastodon's tusk is inferior to that of the Elephant, it is a symbol 

 of inferiority of development ; and inferiority of development is the 

 character of incisor No. i, as compared with incisor No. 2 — size 

 and development being here convertible terms. Now, we have 

 very little comparative knowledge of the dentine of the respective 

 merits of the tusks of the Elephant and Mammoth. The only 

 published information which we know on the subject is two 

 figures of the microscopic structure of each highly magnified, 

 given by Professor Owen in his "Odontography" plates. In these 



