Peterson: Material Discovered in Uinta Basin. 113 



Specific Characters: P~ with tetartocone more distinctly separated 

 from the deiiterocone than in H. hoops; styles at the exit of the median 

 valley of the superior molars smaller; cingula on anterior and posterior 

 faces of upper molars smaller, but larger on the ectoloph near the posterior 

 angle. Animals of same size as II. boops. 



For the present it is thought most prudent to continue to keep the 

 above type specimen under a separate species as established by Marsh. 

 The writer is, however, under the impression that the features of the 

 specimen which vary from those of //. boops may ultimately be re- 

 garded as only representing individual variation. In that case 

 Ilelaletes nanus becomes the type of the genus and //. boops Marsh 

 and " Ilyrachyus" nanus Leidy hypotypes. 



Genus Dilophodon Scott. 

 34. Dilophodon minusculus Scott. (Plate XLIV, Fig. 5). 



Contribution from the E. M. Museum, Princeton, New Jersey, Bull. No. 3, 1883, 

 p. 46, PI. VIII, Fig. 4. 



Type: Right lower jaw, No. 10,019, Princeton Museum Catalogue. 



Horizon: Middle Eocene. 



Locality: Henry's Fork? Wyoming. 



Generic Characters ascertained from the type. /.;, Cj, P-g, ilf-^-. 

 Diastema of the loiver jaiv proportionally shorter than in Ilelaletes boops 

 and rami more sharply constricted back of the incisors and in front of the 

 cheek-teeth; ilfg- ivithoiit hypoconulid; canine small; animal slightly 

 smaller than Ilelaletes. 



There can be comparatively little or no doubt that Dilophodon 

 minusculus pertains to a distinct genus, as originally determined by 

 Professor Scott. The shorter diastema of the ramus suggests a dif- 

 ferent structure of that region than in Ilelaletes. This character 

 together with the absence of a hypoconulid on M^ of the type of 

 Dilophodon is regarded, by the writer as of sufficient generic value, 

 pending the discovery of more complete material. In accepting the 

 genus we avoid attributing two important characters to the genus 

 Helaletes which do not appear to belong to the latter. Beside this 

 fact, it is even possible that Dilophodon represents a third line of tapirs, 

 which may represent a closer relation to the Oligocene and recent 

 tapirs than to those of the Eocene, which are better known. 



Although the dentition of Ilelaletes, Hyrachyus, and Colonoceras 

 resemble one another, the differences between them are obvious on 



8^ — DEC. 16, I919. 



