202 



University of California Publications. 



[Geology 



INTRODUCTION 



In a recent publication, 1 of which the present paper is con- 

 sidered as Part II, the writer has discussed the general features 

 of the formations in the geologic section containing mammal- 

 bearing beds in the region of Virgin Valley and Thousand Creek 

 in northwestern Nevada. The present paper presents such evi- 

 dence as is available regarding the vertebrate faunas obtained 

 from the Virgin Valley and Thousand Creek formations. An 

 attempt is also made to determine the approximate age of the 

 faunas by use of both palaeontologic and geologic criteria of 

 correlation. 



A short list of the most characteristic forms in the fauna of 

 Virgin Valley was published by Merriam 2 in 1907. In 1906 

 Gidley 3 discussed a number of the most characteristic ungulate 

 species from the collections of the University of California. In 

 1910 Furlong 4 described a peculiar aplodont rodent from Virgin 

 Valley, this form being the earliest known representative of the 

 true aplodonts. In a recent paper Miss Louise Kellogg"' has 

 presented a description of the entire representation of the 

 rodent group in the formations of Virgin Valley and Thousand 

 Creek. Excepting the papers just mentioned, so far as the writer 

 is aware, there are no published references to the vertebrate 

 fauna of this region. 



Although the collections from Virgin Valley and Thousand 

 Creek furnish a most interesting representation of the mam- 

 malian fauna which inhabited these regions in late Tertiary time, 

 the number of specimens obtained is relatively small compared 



> Merriam, J. C, Tertiary Mammal Beds of Virgin Valley and Thou- 

 sand Creek in Northwestern Nevada, part I, Univ. Calif. Publ. Bull. Dept. 

 Geol., vol. 6, pp. 21-53, 1910. 



2 Merriam, J. C, Science, n.s., vol. 26, pp. 380-382, Sept. 20, 1907. 



3 Gidley, J. W., Univ. Calif. Publ. Bull. Dept. Geol., vol. 5, pp. 235-242, 

 1908. 



* Furlong, E. L., Univ. Calif. Publ. Bull. Dept. Geol., vol. 5, pp. 397- 

 403, 1910. 



s Kellogg, Miss Louise, Univ. Calif. Publ. Bull. Dept. Geo!., vol. 5, 

 pp. 421-437, 1910. 



