368 FALCONER ON THE TEKDI ISLAND FOSSILS. 



fracture passing through the middle of the last molar, the anterior 

 ridge of which is visible in situ in the jaw. 



The dimensions given below will indicate most distinctly the 

 characters by which this fossil differs from the jaw of the D. 

 giganteum of Kaiip. In relative length, the two agree very closely, 

 the four anterior molars measuring but half an inch more in the 

 Indian than in the European species. But the other proportions 

 are very different. The depth of the jaw measured to the alveolar 

 margin of the second premolar, where the deflexion of the sym- 

 phisis begins alike in both, is 9*2 inches in the former, while it is 

 but 6 *9 -in the latter, and at the back of the third tooth or first 

 true molar, 8*7 inches to 6*2 inches. The Perim fossil exhibits a 

 like excess of dimensions in relative thickness, the jaAY measuring 

 5*1 inches in diameter under the second premolar, and 6'4 inches 

 at the middle of the penultimate molar, while in the European 

 species the corresponding dimensions are respectively 4 and 5 

 inches. In consequence of this great depth and thickness, the jaw 

 of the Indian fossil approaches very closely the massive and turgid 

 form seen in the typical mastodons, such as the 31. giganteus ; while 

 that of the European Dinotherium is comparatively much thinner 

 and more compressed. The inner side of the jaw in the latter is 

 very flat, differing in this respect widely from the mastodons 

 generally : in the Perim fossil this flatness is much less, not ex- 

 ceeding that of the Mastodon giganteus, and behind the body of 

 the jaw bulges out on either side, so as to yield nearly a circular 

 outline in section, and exactly to represent the form in the 

 American Mastodon. This resemblance is so great, that in the 

 absence of the crowns of the teeth, and from its huge proportions, 

 the fossil, when presented to the Museum, and up to this time, has 

 always been regarded as the jaAv of a Mastodon. The relationship 

 indicated by the shape of the jaw, is further borne out by the 

 form and structure of the penultimate lower tooth, as described in 

 the preceding part of this paper. The enamel, which is thinner 

 in the D. giganteum, is as thick in the Indian species as in the 

 lower penultimate of the American mastodon : the outline of the 

 ivory ridge beneath the enamel is the same in both ; the crown ridges 

 have the same transverse, continuous, crenulated, and trenchant 

 form ; and what is most important and significant of all, the hind 

 talon, in respect of form, amount of development, and the character- 

 istic crenulation of its edge, is so precisely similar that this part in 

 the one exactly represents the corresponding part of the same tooth 

 in the other. The same direction of affinity is further indicated by 

 the nearly horizontal line of protrusion and horizontal plane of wear 

 in the teeth, by the form of the ramus, coronoid process, and angle of 

 the jaw, and by the absence of antero -posterior curvature in the 

 outline of its lower surface, in all of which particulars the Ameri- 

 can Mastodon deviates widely from its congeners, and from the 

 Elephantine type generally, and approximates towards the Dino- 

 therium. This tendency is also shown in the very reduced 

 formula of the teeth ridges, in the deflexion of the symphisis, 



