No. 3.] OSTEOLOGY OF MESOHIPPUS AND LEPTOMERYX. 345 



are covered with a finely wrinkled and minutely tuberculated 

 enamel. 



The milk dentition is decidedly traguline in character. Z? 4 is 

 molariform, but very small, and the median internal and external 

 pillars feebly marked ; d s consists of three external cusps, of 

 which the anterior is very long, compressed, and trenchant, 

 which is much larger than in Tragidus, and a small postero- 

 internal crescent, from which a faint ridge runs forward ; this 

 ridge is also better developed than in Traguliis. Lfi is com- 

 posed of three pairs of crescents, of which the anterior pair are 

 quite small and much like the talon of m 8 . D z is much like 

 the premolar which succeeds it in the permanent set. 



The dentition of Leptomeryx is on the whole most like that 

 of the tragulines, especially in the construction of the molars 

 and the milk dentition ; on the other hand, the incisors are very 

 different, and the premolars much more complex, though less 

 so than in the Cervidce. 



II. The Skull. 



The skull of Leptomeryx is peculiar in several respects, and 

 with many points of resemblance to that of the chevrotains, 

 presents almost as many differences. As in the primitive 

 ungulates generally, the cranium is long, narrow, and low, the 

 eye very far forward in the face. The occiput is low, and the 

 upper contour of the skull curves regularly upward and forward 

 to a point just behind the orbits and thence downward to the face. 

 The orbits are rather smaller than in Tragulus, are situated 

 higher in the face, and project somewhat more strongly outward. 

 As in that genus, they are very deep and are posteriorly sepa- 

 rated only by a thin interorbital septum, so that the optic 

 foramina are nearly or quite confluent — a peculiarity which is 

 shared by some of the small antelopes and by Poebrotherinm. 



There appear to be two types of skull represented among the 

 specimens : in one, that figured by Leidy (No. 33, PI. XIV.), 

 the occiput is low and rather broad, and the sagittal crest is 

 very short, hardly longer than in Tragalus. The second type, 

 which perhaps belongs to a species as yet unnamed, has a 

 higher, narrower occiput, and a much longer sagittal crest with 

 narrower forehead and less abruptly diverging supraciliary ridges. 



