No. 3.] OSTEOLOGY OF MESOHIPPUS AND LEPTOMERYX. 343 



Traguhis, but the median ridge is much more pronounced and 

 the depressions in front of and behind it much deeper. A more 

 important difference is in the large internal cusp (deuterocone) 

 which in Traguhis is a mere rudiment. Pm. 3 is similar, but 

 the deuterocone is still larger, and from its anterior edge there 

 passes a ridge to the outer wall of the crown enclosing a small 

 valley. In some specimens, however, which agree exactly with 

 the typical Leptomeryx in size and in the construction of the 

 upper molars, the premolars are quite as simple as in the tra- 

 gulines. Pm. 4 is of the typical ruminant pattern, consisting of 

 an internal and an external crescent ; the horns of the inner 

 crescent are separated from the outer wall and are connected 

 with it only at an advanced stage of wear. 



The outer side of the tooth resembles that of the preceding 

 premolars. 



The molars are composed of four crescents and closely re- 

 semble those of the smaller deer. They differ from the molars 

 of Traguhis in the greater thinness and compression of the 

 crescents, and in the presence of well-developed 'basal pillars 

 between the internal lobes ; the median and anterior external 

 pillars are also very prominent, while in Traguhis the anterior 

 one is but feebly developed, and the median one is absent. In 

 Dorcatherium (Hycemosckus), on the other hand, the external 

 pillars are very well marked, but here there is no internal pillar 

 and the lobes of the tooth are more massive and conical, less 

 completely crescentoid than in Leptomeryx. In the latter the 

 internal crescents are separated from each other in the unworn 

 tooth by a considerable interval. The valleys are perfectly 

 simple, and not complicated by any projections from the walls. 

 The inner side of the crown is covered with a very finely 

 wrinkled enamel, but the external side is smooth and polished. 

 The cingulum is confined to the anterior and posterior faces 

 of the crown. 



2. Lower Jaw. The incisors are somewhat peculiar and not 

 at all traguline in character. The median incisor is procumbent, 

 long, straight, and narrow ; in shape it is more like that of 

 MoscJius than that of the deer or chevrotains, but is very much 

 narrower, more elongate, and very different from the corre- 

 sponding tooth in Traguhis. The second and third incisors 

 are shorter, somewhat more spatulate, and are curved toward 



