58 PACHYDERMATA. 



Kaup), with the exception of figs. 1 and 2, of pi. 1. fig. 11, of pi. 

 2. and fig. 14, of pi. 3., which are probably to be referred to 

 M. angustidens. 



We have already stated the grounds (ante p. 21,) upon 

 which von Meyer, following up the observations of Croizet and 

 Jobert, distinguished M. Arvemensis from M. angustidens, and 

 that Kaup was led by his researches to the same conclusion. It 

 would appear, from a communication in Bronn's Lethsea, that the 

 ridge formula which Kaup attributed with doubt, to M. angusti- 

 dens is jjqor^ in the deciduous series, and 3 ? ~\ 4 1 4 in the true 

 molars. 1 



M. de Blainville has entered at great length, in his Osteographie, 

 on what had been previously written regarding M. angustidens, 

 and he has given a beautiful series of illustrations of all the teeth 

 in succession, in both jaws, as he conceives them to be developed 

 in this species. The rich collection of specimens, discovered by 

 M. Lartet, and others, in Gascony and along the flanks of the 

 Pyrenees (a large portion of which is displayed in the palseonto- 

 logical gallery of the Paris Museum) furnishes ample materials 

 for establishing the specific independence of M. angustidens and 

 M. longirostris. But M. de Blainville has not attached sufficient 

 importance to the constancy of the ridge formula : he has through- 

 out his illustrations intercalated Eppelsheim teeth of the latter 

 species, having four ridges, with Gascon specimens of the former, 

 having three ridges. In consequence, the teeth of the two species 

 are not merely intermixed, but a wrong position in the jaw is in 

 many instances assigned to M. Lartet's specimens of the true 

 M. angustidens. This remark applies, without exception, to the 

 determinations of the two last teeth of the upper jaw. Giving a 

 numerical expression to M. de Blainville's descriptions of the 

 different teeth, the ridge formula in M. angustidens would be 



2 + 2 + 3' 3 + 4 + 6 * respectively, in the three deciduous, and three 

 true molars, on each side of both jaws. It is apparent that the 

 lower numbers do not coincide with the upper, and that, followed in 



1 Lethsea Geognost. p. 1239. 



