ELEPHANT AND MASTODON. 39 



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 continued 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 diminished in thickness and is 

 less uniform in outline, and the surface in contact with the cement 

 shows a feathered or ragged edge, indicating superficial inequali- 

 ties 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. 6 a, the principal 

 difference being that the ridges are narrower, with a greater vertical 

 height. The cement substance attains its maximum of develop- 

 ment 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, represents a corresponding section of a portion of the 

 last molar of the 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, in the elongated cuneiform ivory ridges, unequal enamel, 

 and abundant cement, the differences being merely such as con- 

 stantly 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. 

 Fig. 4 a, 1 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 



1 We are indebted to the kindness of Mr. Charles Stokes for the specimens which 

 have yielded the sections A a and 46 of the African Elephant, the teeth of this species 

 being comparatively rare in English collections. 



