1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 445 



hardly sufficient to warrant speaking with positiveness concerning the 

 age of the beds, but the species were considered as certainly Tertiary 

 and seemed to belong to the Eocene. Both species were stated to have 

 quite a wide geographic distribution and with several unimportant 

 exceptions to be confined to the Eocene. 



At the writer's request the old coal workings on Black Mountain 

 were recently examined by J. P. Buwalda who reports upon them 

 as follows : 



The location of the old coal workings is about two miles to the southeast of 

 Black Mountain, and in the saddle between that mountain and the main El Paso 

 Range. The coal mines were worked at least 12 or 15 years ago. There is only 

 one shaft available and that can no longer be entered. The coal seen in this 

 locality is at the base of the sedimentary series. The Eicardo here lies on a 

 metamorphosed complex quite certainly of pre-Cretaceous age. It is not possible 

 to say certainly that the leaf formation is a member of the Eicardo formation. 

 It might be a freshwater formation deposited upon the metamorphosed complex 

 of the El Paso Eange in early Tertiary time, and the Eicardo beds may be of 

 later date deposited uneonformabty upon it. The stratigraphic relations around 

 the coal mine are not clear. 



The dump from the coal mine has been burned over so that no solid material 

 is left. A few impressions of two or three plants resembling rushes were found 

 but no determinable specimens were obtained. 



Near the extreme western border of the Mohave Desert area the 

 Eocene is represented by marine deposits of the Martinez or Lower 

 Eocene stage. 18 " This section has an estimated thickness of at least 

 5000 feet. How far the marine Eocene deposits extended over the 

 Mohave area originally is not known. It is possible that land or fresh- 

 water beds were accumulating in this area contemporaneously with 

 the marine Eocene, or the sea may have covered a considerable portion 

 of the area. No marine deposits of later age than Eocene are known 

 in the Mohave area. 186 



Barstow Syncline Section. — The section in the Barstow syncline 

 consists in a large part of volcanic materials with beds of clay and 

 shale at some horizons. The deposits are evidently partly of terres- 

 trial and partly of lacustrine origin. At rare horizons, ^remains of 

 fresh water mollusca including Planorbis and Anockmta ( ? ) are 

 abundant. In other beds scattered and weathered bones, representing 

 a large tortoise and numerous mammals belonging to the open plains 

 type probably indicate accumulation on dry land. Baker held that 



18a Diekerson, E. E., Univ. Calif. Publ., Bull. Dept. Geol., vol. 8, p. 293, 1914. 



isft Since this paper was written Wallace Gordon has discovered marine beds 

 of middle Tertiary age on the western border of the Mohave area near Quail Lake, 

 35 to 40 miles west of Lancaster on the main line of the Southern Pacific Eailroad. 



