MASTODON ARVERNENSIS. 29 



angustidens of Siraorre. In the Eppelsheim species, of which 

 I have carefully examined all the molars contained in the rich 

 collection at Darmstadt, there is a considerable range of 

 variety, as regards the accessory tubercles which flank the 

 main ridges. In some of the last molars, the main ridges are 

 perfectly free from any outlying or flanking mammillse ; they 

 are regularly transverse, and the valleys between are equally 

 transverse, and open throughout. In others, the ridges bear 

 numerous small warty tubercles of enamel, which jut into the 

 valleys and distort them. But the transverse continuity of 

 the valleys is never blocked up by the large conical mastoid 

 mammillse, which in the molars of M. (Tetralophodon) Arver- 

 nensis invariably alternate with the main ridges, and reduce 

 the valleys to disconnected gorges, occupying the outer and 

 inner sides of the crown. The accessory tubercles in the 

 Eppelsheim species are so unimportant, that their only effect, 

 after advanced wear, is to expand the diameter of the disc, 

 or communicate to it something of a trefoil pattern. The 

 discs are always transverse, while in the English Crag Mas- 

 todon they are invariably more or less alternate. In illustra- 

 tion of this very obvious differential character in M. 

 (Tetralophodon) longirostris, the beautiful series of figures given 

 by Kaup in the ' Ossemeus Fossiles de Darmstadt,' from 

 Plates XVI. to XXI. inclusive, may be quoted ; but I would 

 more especially refer to figs. 4 and 5 of PI. XVI., figs 1, 3, 4, 

 and 9 of PI. XVIIL, and figs, 2, 6, and 7 of PI. XXI. 



We have endeavoured to exhibit these differences in a 

 well-marked and obvious manner, by contrasted figures 

 (drawn with the greatest care and fidelity by Mr. George 

 Ford) of the same tooth in three species, placed side by side, 

 in Plate XXXVI. of the ' Fauna Antiqua Sivalensis.' Pigs. 6 

 and 6 a 1 represent in plan and profile the last molar (upper jaw, 

 left side) of If. (Tetralophodon) Sivalensis, an Indian fossil spe- 

 cies, which is the most nearly allied to the English Crag Mas- 

 todon, so far as the alternate disposition of the crown-mam- 

 millae is concerned, but differing in the ridge-formula. Figs. 8 

 and 9 represent two specimens of the same tooth of M. (Tetra- 

 lophodon) Arvernensis, the one being Mr. William Smith's 

 Whitlingham fossil, and the other (fig. 9) Captain Alexander's 

 specimen, dredged up between Southwold and Easton, of 

 which there is a cast in the Geological Society's Museum. 

 Figs. 12 and 13 represent two specimens, of different races 

 or sexes, of the same tooth of M. (Tetralophodon) longirostris, 

 from Eppelsheim. The Sewalik molar (fig. 6) exhibits six 

 ridges and a hind ' talon ; ' the Crag and Eppelsheim molars 



1 See vol. i. Plate ix. figs. 1 and 2.— [Ed.] 



