2(52 G. T. BETTANY Otf THE GENUS MERYCOCBXERTJS. 



as it gives rise to an erroneous conception of the nature and appear- 

 ance of these teeth. 



The following are the distinctive characters assigned by Prof. 

 Leidy to the genera of Oreodontidae established by himself (" Con- 

 tributions," pp. 201, 202). 



" Oreodon : Molar teeth with short crowns, as in the deer, and, as 

 in this, at maturity inserted by fangs. Anterior premolars straight, 

 with the diameters nearly equal, and with their points median or 

 nearly so. Face gradually convergent, conical. Infraorbital arch 

 narrow or of moderate depth, gradually declining upon the side of 

 the face. Infraorbital foramen small and situated above the third 

 premolar. Nasal orifice nearly as wide as high, and situated imme- 

 diately above the incisive alveolar border, as usual in most animals. 

 Premaxillaries and maxillaries remaining distinct from one another. 

 Incisive foramina of moderate size. 



u Merycochcerus : Crowns of the molars proportionately longer than 

 in Oreodon, and protruding gradually as they were worn away, the 

 anterior having their sculptured triturating surface obliterated before 

 the posterior are fully protruded. Anterior premolars with the 

 length and breadth exceeding the width, and the upper ones incli- 

 ning posteriorly, and with their points in advance of the middle. 

 Facial cone abruptly narrowed in advance of the orbits. Infra- 

 orbital arches deep and rapidly declining on the face. Orbits 

 smaller and more externally situated than in Oreodon. Infraorbital 

 foramen above the interval of the first and second molars. Nasal 

 orifice situated far above the alveolar border, as in the tapir, and 

 commencing below as an angular notch of the premaxillaries, which 

 are firmly coossified together and with the maxillaries. Incisive 

 foramen large. 



u Merychyus : Teeth as in Merycochcerus. Facial cone intermediate 

 in character to the latter and Oreodon. Infraorbital foramen 

 situated above the last premolar, or in a position intermediate to 

 that of Oreodon and Merycochcerus T 



The following corrections must be made in the generic characters 

 of Merycochcerus, in consequence of the greater perfection of our 

 specimens : — 



1. The facial narrowing in front of the orbits is very little greater 

 or more sudden in Merycochcerus than in Oreodon, although it is 

 considerable. 



2. The orbits are not relatively smaller than in Oreodon. 



3. The position of the infraorbital foramen relatively to the 

 teeth seems to be variable. In our specimens it is above the 3rd 

 premolar, or the interval between the 3rd and 4th. 



4. The nasal orifice extends far above the alveolar border, and ap- 

 pears to be uninterruptedly open from the apex of the notch between 

 the premaxillaries, only half an inch above their continuous alveolar 

 border, to the horizontal projecting spine of the connate nasals. 



Since the position of the infraorbital foramen varies in different 

 species, the genus Merychyus may very well be dropped, as it is 

 founded upon this single character. The teeth and portions of jaws 



