414 University of California Publications in Geology [Vol. 9 



marine Miocene formations of the Coast Ranges are carefully com- 

 pared with those of the Sierran andesitic tuffs. 



The determination of the age of the rhyolitic and interrhyolitic 

 channels as Eocene differs from previous age determinations. The 

 previous evidences of age were vertebrate remains and floras from the 

 bench gravels and rhyolitic tuffs. Unfortunately the vertebrate local- 

 ities are uncertain. Lindgren says : 



The number of species of clearly prevolcanic occurrence is not large. 

 The most important localities are Douglas Plat and Chili Gulch, in Cala- 

 veras County, and the Tuolumne Table Mountain not far to the south, 

 in Tuolumne County. In the Calaveras County localities bones and teeth 

 of a species of rhinoceros, described by Leidy under the name of R. 7i.es- 

 perius, have been discovered. At Douglas Flat was also found a tooth of 

 the pachyderm Elotherium, which belongs to the Eocene or Oligocene 

 (White River Group of the Rocky Mountain region) . . . These few 

 occurrences complete the list of fossils which Whitney considered authentic 

 and beyond doubt derived from the Tertiary gravels. 



The forms might represent either Oligocene or Eocene species. 



Knowlton 62 who has studied all of the floras of the West Coast 

 described the life conditions of the flora of the auriferous gravels 

 in a note to Diller as follows : 



Lesquereux, as you have already stated, argued that the presence of 

 a large number of lauraceous plants indicated a region analogous in at- 

 mospheric conditions to Florida. From my own studies which embrace 

 a much larger amount of material than Lesquereux had, I am not only 

 prepared to accept this .statement, but to show that it now has stronger 

 support than he could have given it. Lesquereux knew only about 50 

 species of plants in the auriferous gravels, whereas the present known 

 flora embraces nearer twice that number. Of this number the following 

 genera are distinctly tropical or subtropical in their distribution: Laurus 

 (4 species), Per sea (3 species), Cinnamomum (2 species), and Oreodaphne 

 (2 species), all belonging to the Lauraceae. In addition to these there 

 is Artocarpus and Zizyphus, each with 2 species, Ficus with 6 species, 

 and Sabalites with 1 species, or 22 species in all, representing at least 

 20 of the entire present flora. The present flora of Florida has only' 5 

 genera and 8 species belonging to the Lauraceae, which represent less 

 than one per cent of the whole flora, while, as stated above, there are 4 

 genera and 10 species in the auriferous gravels, representing fully ten 

 per cent of that flora. 



Following is a list of genera, with the number of species in each 

 having living representatives confined in the main to temperate regions, 

 some of them growing at elevations at or but little above sea level: Aralia 

 (4), Platanus (2), Cornus (4), Juglans (5), Liquidambar (1), Magnolia 

 (4), Quercus (15), Viburnum (3), Rhus (6), Alnus (3). Of course it is 

 quite impossible to say that these species actually grew at the above alti- 



62 Knowlton, F. H., in Topographic Revolution on the Pacific Coast, Four- 

 teenth Annual Report, U. S. Geological Survey, Part II, p. 421, 1894. 



