430 



TJ: 



niversity of California Publications. 



[Geology 



In the number and arrangement of the lakes, nos. 11843, 

 11684, 11540 correspond to Mylagaulus pristinus Douglass as 

 figured in the Annals of the Carnegie Museum. 4 They also agree 

 in size, except for the height of no. 742, which is greater on 

 account (if its being an unworn tooth, while these specimens are 

 those of old individuals with roots closed at the bottom. No. 

 12579 is an unworn tooth very much like P 4 of fig. 265. 



Eucastor (Sigmogomphius) lecontei was described as gener- 

 ically different from Eucastor tortus Leidy on account of the 

 open character of the folds, the relatively greater size of the 

 molars, the relatively small size of the triturating surface of P 4 , 

 and the absence of M s . In his description of Eucastor, Leidy 

 makes no reference to a third molar, although the figure shows 

 what is perhaps an alveolus for a fourth tooth on the right side. 

 As the presence of isolated lakes instead of open folds is an age 

 character, we may say that Sigmogomphius is specifically differ- 

 ent from Eucastor tortus on account of the relatively greater 

 size of the molars and the relatively small size of the triturating 

 surface of P\ but that there does not seem to be sufficient 

 evidence to separate them generically. 



A specimen, no. 11085, a right P 4 , from locality no. 1090, 

 Virgin Valley, Humboldt County, Nevada, is so close to Eucastor 

 lecontei that it can hardly be separated from it specifically, 

 although it is a more nearly square tooth, P 4 of E. lecontei being 

 triangular with the apex at the inner posterior corner. 



Measurements. 



P 4 , anteroposterior diameter 



P 4 , transverse diameter 



P 4 , height 



No. 12570 No. 11848 No. 11684 No. 11540 



7.2 mm. 7.0 mm. 7.4mm. (5.7mm. 



4.5 3.7 4.3 3.9 



17.2 10.8 11.3 11.3 



EUCASTOR LECONTEI (Merriam). 

 Fig. 13. 



Measurements. 



E. lecontei 

 No. 11085 Type 

 specimen 



P 4 , anteroposterior diameter 

 P 4 , transverse diameter 



4.6 mm. 4.7 mm. 

 4.9 5.1 



■* Ann. Carneg. Mus., vol. 2, p. 188, fig. 26c (no. 742). 



