76 FAUNA ANTIQUA SIVALENSIS- 



greater than the width of their base. The interspaces of the 

 plates are proportionally deep and filled up with a copious 

 mass of cement, which completely envelopes the tooth. The 

 quantity of this substance is measured by the projportion 

 which it bears to the other dental materials, and it is seen to 

 be thicker than the ivory plates. The layer of enamel is 

 reflected over the ridges and down upon the hollows, as in 

 jE/. insignis, but it is much thinner, and the attenuation is 

 proportioned to the elongation of the plates. The common 

 basal mass of ivory is greatly reduced in quantity, if com- 

 pared either with the sections of E. insignis, fig. 1, or of 

 E. planifrons, fig. 2, there being little more of this substance 

 than is sufiicient to establish a common connection between the 

 bases of the segments, and a foundation for the offset of the 

 fangs, which are numerous. The vertical height of the tooth 

 is considerably greater than that of either of the two other 

 described sjDecies. The tooth measm-es 8-7 inches in length. 

 Fig. 4 I, PL II., r.A.S., represents a pentiltimate molar of 

 the lower jaw of the same species in vertical section. Like 

 that of the upper jaw, it is composed of nine cuneiform plates. 

 This tooth had been a long time in use, all the jplates except 

 the last being affected by wear. The anterior part of the 

 crown has been ground down to nearly one-third of its original 

 height, so that the enamel divisions between the two anterior 

 ivory plates have disappeared, and the latter are confluent 

 into a common mass. It is not, therefore, in the condition 

 best adapted to show the characters presented by a good 

 section ; but it indicates sufiiciently the correspondence of 

 the lower with the ujjper molars, in the disposition, form, 

 and relative proportion of the ivory, enamel, and cement 

 substances. It bears a very close resemblance to the section 

 of the lower molar of E. ]}lanifrons, fig. 5 h, keejDing in mind 

 that the latter is taken from an older and larger tooth. 

 They exhibit the same kind of wedge-shaped ivory plates, a 

 similar amount of cement in the interspaces, and an analogous 

 thickness of enamel. The resemblance between the lower, in 

 these instances, is greater than between the corresponding 

 upper molars of the two species. This specimen measures 

 7*2 inches in length. 



If the eye is carried along these sections in succession, it 

 will be readily perceived that they constitute a series of 

 gradations in form conducted from E. insignis to E. Afrieanus, 

 through E. planifrons. The modifications are effected by the 

 elongation and thinning of the ridge-plates, with a corres- 

 ponding increase in the depth of the hollows, and in the 

 vertical height of the teeth ; by a diminution of the basal 

 mass of ivory ; by a greater number of divisions in the same 



.1! 



