Vol. 6] Merriam: Virgin Valley and Thousand Creek. 



283 



shelf appears on the figured specimens which the writer finds 

 referred to Palaeomeryx or Dromomeryx. 



The shelf on the cingulum is strongest next the mesostyle, 

 and disappears opposite the middle of the outer side of the para- 

 cone. A similar shelf appears to be shown on the larger form 

 described by Gidley, but it seems to the writer to be due in some 

 part at least to a fracture of the specimen. On two other upper 

 molars of the larger form from Virgin Valley there is no sugges- 

 tion of this shelf. 



The possibility that the first two of the upper molars of no. 

 11470 described above represent the milk dentition has been 

 considered, but the evidence does not seem to indicate that this 

 is the case. Even if this were true, it should be noted that the 

 shelf of the cingulum described above is shown on the most pos- 

 terior tooth, as well as on the others, and would still be a char- 

 acteristic of the permanent dentition. 



A shelf of the type seen in the smaller form is barely sug- 

 gested on a large worn specimen of Dromomeryx from the Mas- 

 call Beds of Oregon. 



Measurements 



No. 11470 



Length, anterior side M 1 to posterior side M 3 44.3 mm. 



M 1 , anteroposterior diameter 14.3 



M l , transverse diameter 18.5 



M J , anteroposterior diameter 16.0 



M 2 , transverse diameter 20.3 



M 3 , anteroposterior diameter 15.8 



M 3 , transverse diameter 19.0 



DROMOMERYX, sp. 

 In the collections from Virgin Valley there is a specimen 

 consisting of the basal portion of a large horn-core, no. 11628 

 (figs. 63a and 63&), the form of which shows close resemblance 

 to Dromomeryx. The portion of the horn present is nearly 

 straight, with only a suggestion of curvature, and narrows 

 gradually from the base upward. The basal portion of the core 

 is triangular in cross-section. The section of the terminal 

 region seems to have been approximately oval. The texture of 

 the surface of the core is in general more dense or less pitted 

 than in Aplocerus. 



