386 SOLIPEDIA. 



similar character appears to have been recognized by 

 M. H. v. Meyer in some of the fossil equine teeth from the 

 Eppelsheirn sand, since he cites the Equus angustidens as 

 a synonyme of the species which he subsequently described 

 under the name of Equus asinus primigenius.* 



The upper molar teeth of the Horse resemble those of 

 the Palseotherium in the two deep longitudinal channels (d 

 d, fig. 143,) which traverse their outer side, but the enamel- 

 linings of those channels are not produced into points on 

 the grinding surface. This surface of the equine molar 

 also presents a close analogy with that of the Rhinoceros ; 

 to aid in tracing which, the corresponding but modified 

 folds and islands of enamel in the complex molar of the 

 Horse (fig. 143) are marked with letters corresponding 

 with those on the upper molar of the Rhinoceros lep- 

 torMnus (fig. 141). For the details of the character- 

 istic structure of the teeth of the genus Equus-, which 

 would be unsuited to the present work, I must refer the 

 reader to the * Ossemens Fossiles, 1 and to my ' Odon- 

 tography' ; and here merely add, that the character by 

 which the Horse^s molars may best be distinguished from 

 the teeth of other Herbivora, corresponding with them 

 in size, is the great length of the tooth before it divides 

 into fangs. This division, indeed, does not begin to take 

 place until much of the crown has been worn away ; and 

 thus, except in old Horses, a considerable proportion of 

 the whole of the molar is implanted in the socket by an 

 undivided base. In an old molar with roots, the pattern 

 of the grinding surface, as it is shown in the figs. 142 

 and 143, is a little changed by partial obliteration of the 

 enamel folds, but enough generally remains to serve, 

 with the form of the tooth, to distinguish it from the 

 rooted moiar of a Ruminant. 



' Palaeologica,' p. 80. 



