68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



verse diameter of these teeth as a consequence of the angle they are 

 turned to the plane of the palate. 



A feature not so evident in either Protoreodon or other Diplo- 

 bunops material is the more noticeable pocketing or distinct basining of 

 the anterolingual portion of the posterior lower premolars. In P3 

 this may be largely due to crushing although it seems clear that there 

 was a lingual rim along this portion of the tooth. In P4, though like- 

 wise distorted by crushing, the basin appears more clearly defined. 



OROMERYCIDAE, new family 



The genera grouped in this very distinctive family include Oro- 

 meryx, Protylopiis, Camelodon, Malaquijenis, and Eotylopus. It is 

 characterized as distinct from the Camelidae in comprising compara- 

 tively short-snouted forms in which the teeth are more brachydont. 

 The upper molars exhibit a protocone which bifurcates posteriorly, 

 and the external ribs and mesostyle are strongly developed. The lower 

 molars are peculiar in that the conical entoconid is distinctly isolated 

 from the metaconid by a deep pocket which opens through a notch 

 in the lingual wall of the tooth. 



The name Oromerycidae is selected rather than one derived from 

 Protylopus or Eotylopus, although these forms are better known, 

 because Oromeryx is the oldest available name and there is a strong 

 probability that Protylopus may eventually prove to be a synonym. 

 Moreover, both Protylopus and Eotylopus give unwarranted and un- 

 desired suggestion of a relationship to the camelids. 



The oromerycids would appear to be camelids in certain respects, 

 particularly in the character of the lower premolars, the scarcely 

 emphasized canines, and the procumbent lower incisors. In the pre- 

 molars there are points of resemblance to the leptotragulids as well, 

 but the first premolar below is not caniniform. The molars, usually 

 considered to be the more-conservative structures, are highly distinc- 

 tive and raise considerable doubt as to camelid as well as leptotragulid 

 affinities of this group. Although Scott (1940) called attention to the 

 many noncamelid-like structures and appearances of the Eotylopus 

 skull and skeleton, he, unlike Matthew (1910), placed it in the 

 Camelidae. Actually, Eotylopus is superficially more camel-like than 

 Protylopus, but the resemblance is in characters which may be of no 

 more than adaptive significance. It seems clearly evident that certain 

 of the similarities are to be accounted for by convergence, and the 

 basic relationship of the oromerycids is not so close to the camelids as 

 the adaptive parallelism shown in the later form tends to suggest. 



