342 SCOTT. [Vol. V. 



examination reveals the connection very clearly. This simi- 

 larity extends also to the earlier members of the equine series, 

 for Hyracotherium from the lower Eocene belongs as unmis- 

 takably to this line as do any of the later genera. Indeed, one 

 of the most striking features of this phylum is the way in which 

 its essential features, and even many apparently insignificant 

 details, are, as it were, sketched out in very early times and 

 then gradually elaborated, without deviation and without retro- 

 gression, until the final term of the series is reached. 



THE OSTEOLOGY OF LEPTOMERYX EVANSI LEIDY. 



This problematical little selenodont is very abundantly repre- 

 sented in the White River beds by fragments of jaws and teeth ; 

 but owing to their small size and extreme fragility, well pre- 

 served skulls and parts of the skeleton are very rare. However, 

 by combining the material contained in the Princeton Museum 

 with that in the Academy of Sciences in Philadelphia, and some 

 beautifully preserved specimens which Professor Cope has most 

 kindly placed at my disposal, I am enabled to give a fairly com- 

 plete account of the structure of this genus. 



I. The Dentition. 



i. Upper Jaw. The skulls of all the specimens which I have 

 examined are broken away anteriorly, so that the premaxillary 

 region is lost, and it is therefore impossible to say whether Lep- 

 tomeryx had any remains of upper incisors, but from the char- 

 acter of the lower incisors it seems probable that the superior 

 set had vanished. From the analogy of Amphitragidus and the 

 tragulines, it might seem likely that the upper canine, at least in 

 the males, was a long, recurved blade. But, on the other hand, 

 no such tooth has ever been found associated with Leptomeryx 

 remains. None of the specimens shows any trace of the first 

 upper premolar, and if present at all, it must have been sepa- 

 rated by a considerable diastema from the second. Pm. 2 is a 

 sharp, compressed, cutting blade, which seen from the outside 

 has a considerable resemblance to the corresponding tooth of 



