ELEPHANT AND MASTOEON. 



75 



The next serial modification in tlie disposition of the 

 three dental substances, and in the consequent form of the 

 teeth, is exhibited (in fig. 5 a of the same plate, F.A.S.) in 

 Plate IV. fig. 2, which represents a section of the penultimate 

 upper molar of another Indian fossil species, which we have 

 named E. planifrons. This tooth shows nine ridges, the 

 three anterior of which alone have been in use, the two first 

 being worn down to a single disc of ivory. The common 

 nucleus of this substance is of less thickness than in the 

 corresponding tooth of E. insignis, and the divisions which 

 are contmued upwards from it into the centre of the ridges 

 are more elongated, with a narrower base, forming irregular- 

 shaped wedges. The layer of enamel is dimuiished in thick- 

 ness and is less uniform in outline, and the surface in contact 

 with the cement shows a feathered or ragged edge, indicating- 

 superficial inequalities for the firmer cohesion of this latter 

 substance. The enamel is reflected over the ridges of ivory, 

 and down into the hollows zig-zag wise, exactly as in fig. 1, 

 the principal difference being that the ridges are narrower, 

 with a greater vertical height. The cement substance attains 

 its maximtim of development in this species, completely 

 filling up the wide interspaces of the ridges, over which it is 

 continued in a thick mass. This tooth measures 8" 7 inches 

 in length. 



, Fig. 5 b, F.A.S. , represents a corresponding section of a 

 portion of the last molar of tlie lower jaw of the same species, 

 comprising nine ridges. This tooth had been longer in use 

 than that of the upper jaw, and all the ridges are more or 

 less worn, except the two last. It presents the same general 

 characters exhibited by fig. 5 a (PI. IV. fig. 2), in the elongated 

 cuneiform ivory ridges, unequal enamel, and abundant cement, 

 the differences being merely stich as constantly hold between 

 molars of the upper and lower jaws and of different ages, in 

 the same species. 



The existing African elephant furnishes another link in the 

 chain of modifications presented by the molars in this family. 

 Plate IV. fig. 3 (PI. II. fig. 4a, F.A.S.') shows a section of the 

 penultimate grinder of the upper jaw of this species, which 

 is composed of nine principal divisions and a subordinate 

 ' talon ' ridge, the four anterior of which are partly worn, the 

 rest being entire. The elongation of the ivory segments, 

 which commences in E. planifrons, is carried here to a much 

 greater extent. The segments are produced into long narrow 

 wedge-shaped plates, the height of which is many times 



' We are indebted to the kindness of 

 Mr. Charles Stokes for the specimens 

 which have yielded the sections 4 a and 



4 b (PL II. E.A.S.) of the African ele- 

 phant, the teeth of this species being com- 

 paratively rare in English collections. 



