DESCEIPTION OP PLATES. 425 



and the hollows between the ridges are very wide and open, being 

 almost rounded at the bottom. There is only an exceedingly thin crust 

 of cement, continued over the fangs in greater thickness. The common 

 plane of the grinding ridges of the crown is nearly horizontal. M. 

 Ohioticus constitutes the terminal link in the chain, and through 

 Dinotherium establishes a passage into the ordinary Pachydermata. — 

 B.M. (Reproduced in Plate VII. fig. 2.) 



Fig. 10 a. — Mastodon Sivalensis, from the Sewalik hiUs. Vertical 

 section of last upper molar. The ridges are more complex in their 

 composition than in M. laticlens. The croAvn is bisected by a longitudinal 

 fm-row, each division of the ridge being composed of a pair of contiguous 

 conical mammillae placed more or less alternately. The hollows are in 

 consequence interrupted. There are five principal ridges, with a subor- 

 dinate ridge in front, and a talon ridge behind. Eight divisions of the 

 ivory may be counted in the figure, the smaller segments arising from 

 the dii-ection in which the section has been made through the alternate 

 mammillse. The ridges are approximated, and the enamel bears a 

 large proportion to the conical lobe of ivory which it invests. The 

 cement is entirely wanting, except in the bottom of the clefts. — B.M. 

 (Reproduced in Plate VII. fig. 1.) 



Length of tooth, 7 in. 



Fig. 10 h. — Mastodon Sivalensis. Vertical section of greater part 

 of last lower molar. The tooth differs from the corresponding upper 

 molar only in being complicated with an additional ridge. — B.M. 



Fig. li, — Dinotherium Indicum (Falc), from Perim Island. Ver- 

 tical section of posterior ridge and talon of the penultimate lower 

 molar, left side. The internal structure exhibits the same agreement 

 with that of the European Dinotherirun, as is indicated by the external 

 form. The only perceptible difference is, that the angle formed by the 

 ridge of the ivory is more acute, and the enamel thicker in the Indian 

 species. The centre is occupied by a rhomboidal core of arenaceous 

 matrix marking the form of the unossified pulp nucleus. This tooth 

 is described and figured in Dr. Falconer's Memoir on Perim Island 

 Fossils {Vide page 396, and Plate VI. fig. 3.) 



Fig. 12. — Dinothei'ium gigajiteum (Kaup), from Eppelsheim. Ver- 

 tical section of entire penultimate lower molar, consisting of two 

 transverse crenulated ridges, and a talon ridge, while in the equi- 

 valent molar of Mastodon Ohioticus there are three principal ridges. 

 Corresponding to the smaller number of divisions the ridges are more 

 widely separated, less elevated, and broader at their base, while the 

 interspaces are also wider and more open than in the North American 

 Mastodon. The layer of enamel is of similar thickness, and there is 

 no api^reciable crust of cement. The correspondence is followed out 

 in the form of the subordinate heel ridge. J). Indicum, however, is 

 the species most nearly allied to M. Ohioticus. — B.M. (Reproduced in 

 Plate VII. fig. 3.) 



Plate IV. 



Elephas Hysudricus. (Falc. and Cant.), from the Sewalik hills. Front 

 view of skull, one-fifth nat. size. This fine specimen was purchased 

 from Conductor Dawe. — B.M. 



Length of the cranium from the protuberances of the occipital to the broken tip 

 of left incisive, 45' in. Length from broken occipital condyles to anterior border of 



