272 



University of California Publications. [Geology 



The Virgin Valley specimens comprise a number of scattered 

 limb-bones, and several cheek teeth with a small part of a tusk. 

 All of this material represents a form of the mastodon type, but 

 the specimens are not perfect enough to permit an exact deter- 

 mination. The size of the tooth fragments indicates that the 

 individuals were quite large. A few fragments associated with a 

 specimen found low down in the section at Virgin Valley seem 

 to show an enamel band along the side of a tusk. A series of 

 almost unworn teeth which had broken down and scattered over 

 many square yards of a steep hillside in the Virgin Valley Beds 

 of High Rock Canon was partly recovered and pieced together, 

 so that a portion of the form of the molars can be represented in 

 figures 46 and 47. 



In the Thousand Creek Beds proboscidean remains are not 

 uncommon, though nearly always scattered or badly fractured. 

 A proboscidean jaw with a portion of the skull (pi. 33) found 

 by Miss Alexander in the beds at Thousand Creek was the only 

 specimen obtained that represented more than an isolated ele- 

 ment of the skeleton. This skull had evidently been broken 

 before it was buried, and the part remaining had been unevenly 

 preserved. The teeth and a portion of the jaw were preserved 

 without alteration, though intersected by very numerous frac- 

 tures. The remaining part of the skull had broken down to a 

 soft pulpy mass which could not be satisfactorily preserved. 

 The dentition of this specimen seems to be of a fairly advanced 

 type, and may represent a tetralophodont form. Other material 

 from the Thousand Creek Beds evidently represents the same 

 form as the specimen found by Miss Alexander. 



SUIDAE 



PEOSTHENNOPS(f), sp. 



A number of associated bones and teeth (no. 11876) from 

 Thousand Creek represent a large dicotyline form probably most 

 nearly allied to Prosthennops. No exact comparison with the 

 species of that genus can be made as the parts present in the 

 Nevada material are not well preserved in the available Pros- 

 thennops material. 



