306 University of California Publications in Geology [Vol. 8 



the east side of the Virginia Range, east of Reno, the beds between 

 Reno and Verdi to the west have commonly been considered, and pre- 

 sumably correctly so, as part of the Truckee. 



The determination of the age of the Truckee beds as Miocene by 

 King 4 was based upon a rhinoceros tooth and fresh-water molluscs, both 

 obtained from the Kawsoh Mountains, and upon the general similarity 

 of the Truckee to beds in Oregon, with which they were supposed to 

 be continuous. The Oregon strata were stated to underlie basaltic 

 lavas and their mammalian fauna was considered to indicate a Miocene 

 age. 



The rhinoceros tooth obtained in the Truckee beds was determined 

 as probably representing Rhinoceros (Diceratherium) pacificus Leidy. 

 This species was originally described 5 on the basis of very fragmentary 

 material from a locality of uncertain position, probably within the 

 limits of the John Day Oligocene of eastern Oregon. It is listed by 

 King as occurring in the pre-basaltic beds in Oregon with fourteen 

 other mammalian species, representing a fauna now regarded as 

 Oligocene. There is some doubt as to the correctness of the assignment 

 of the Truckee tooth to the Oregon species. So far as known, no 

 careful comparison has been made. Its present bearing on the age 

 of the Truckee is obviously quite uncertain. 



Regarding the fresh-water molluscs King remarks :" ' ' The fresh- 

 water mollusca of the saccharoidal limestone of Fossil Hill would not 

 alone afford sufficient data for referring this series to the Miocene, 

 although Professor Meek, independently of any other reason, made 

 this assignment." On the following page King states: "The molluscs 

 from Fossil Hill, and the rhinoceros tooth, distinctly refer the Nevada 

 strata to the Miocene." 



King's main reason for considering the Truckee beds Miocene in 

 age was that Professor Marsh had studied, along the John Day. 

 DesChutes, and Crooked rivers in Oregon, a series of tilted deposits 

 lying beneath basaltic rocks, and containing numerous vertebrate 

 remains considered to be clearly of Miocene types; these beds King 

 stated were "apparently the direct northward continuation of the 

 Nevada formation." The list of fifteen mammalian species above 

 mentioned, now recognized as Oligocene forms, was given as having 



* King, Clarence, U. S. Geol. Explor. Fortieth Parallel, vol. 1, pp. 423-24, 454- 

 55, 1878. 



a Leidy, Joseph, Proc. Acad. Nat. Sci. Phila., vol. 23, p. 248, 1871. 



e King, Clarence, IT. S. Geol. Explor. Fortieth Parallel, vol. 1, p. 423, 1878. 



