86 THE MAMMALIA OF THE DEEP RIVER BEDS. 



As compared with the upper molars of the large European AnchitJierium, A. 

 aurelianense, those of Desmaiippus differ in the following respects : (1) The presence of 

 cement in the valleys ; (2) the great widening of the transverse crests, especially of the 

 posterior ones ; (3) the much greater distinctness of the conules, which in the European 

 species are very obscurely marked ; (4) the greater flatness of the external cusps. 



B. Lower Jaw. The first premolar has been lost from the specimen. The 

 second differs considerably from the others in the shape of the anterior half of the 

 crown ; this portion of the tooth is flattened on the outer side and tapers anteriorly, 

 giving it a wedge-like shape, when viewed from above. In consequence of this 

 arrangement, the protoconid is triangular in section, the crests to the para- and deu- 

 teroconids respectively straight instead of curved, and the external valley is wider 

 and of a different shape from that of the other premolars ; the paraconid is larger 

 and the posterior pillar smaller. Seen from the outside, this tooth appears to have a 

 very similar construction to the pTs of MesoMppus, but in a crown view the following 

 differences are to be observed : (1) The proto- and paraconids are connected by a 

 crest ; (2) the anterior internal valley is very much better developed ; (3) an anterior 

 pillar is formed behind the deuteroconid, though both of these elements are much 

 smaller than in the other premolars. In Anchitherium aurelianense the development 

 of this tooth has proceeded farther than in Desmaiippus, but in a somewhat different 

 and peculiar way, the paraconid being greatly enlarged, comparable to the very large 

 anterior buttress of the corresponding upper tooth. 



The third and fourth premolars are molariform. The paraconid is much reduced 

 and not distinguishable as a separate element from the anterior crest; the deutero- 

 conid and anterior pillar are enlarged and of nearly equal size, and though much less 

 distinctly separated from each other than in Protoliippus, they are sufficiently enlarged 

 to narrow the entrances to the internal valleys, which expand on the external side of 

 them ; the posterior pillar is fairly well developed and, when moderately worn, be- 

 comes confluent with the tetartoconid. The latter cusp is simple and does not send 

 forward a crest such as is found in Proiohippus. 



The molars, as in the upper jaw, decrease in size, especially in breadth, poste- 

 riorly, m. a being conspicuously narrower than m. i and, but for its talon, shorter as 

 well. In construction they differ but slightly from the premolars. On iu. l the pos- 

 terior pillar is rather smaller than on pTi, and on m. 2 it appears to be wanting, but 

 m. 3 shows it enlarged and developed into a distinct heel. None of the lower teeth 

 in the type specimen display any indubitable traces of cement ; other isolated teeth, 

 however, which I think should be referred to the same genus, if not the same species, 

 have a very thin coating of this substance. 



