While there is considerable literature on the North American marine fossil diatoms from Cretaceous to Recent, little information has been published concerning the North American non-marine fossil diatoms, especially those of the Miocene. Such classic papers as those of Hanna (1927a and 1927b), Hanna and Grant (1926), and Lohman (1948) treated only marine or brackish diatom fossils. There have been numerous lists and countings of species of non-marine diatoms from various Miocene localities in North America, but none of these are of a detailed taxonomic nature. With the possible exception of the paper of Mann (1926), there has never been a detailed taxonomic report concerning a well dated Miocene non-marine fossil deposit of a specific locality in North America. On the other hand, many of the European and Asian non-marine deposits have been examined in detail by such workers as Heribaud (1893—1908), Lauby (1910), and Krasske (1934-). Also, several Russian papers on fossil non-marine diatoms are of importance, Juravleva (1936), Poretzij (1953a and 1953b) and Proschkina-Lavrenko (1949—1950).
Numerous taxa are reported from the Miocene non-marine deposits of North America for the first time in this paper. More work has been conducted on the Tertiary non—marine diatomite deposits of North America than the literature indicates. The reason for this is that there are few well dated non-marine diatomite deposits in North America. C. G. Ehrenberg (1854—1856), for example, described many non—marine diatomite deposits from North America but gave little indication of their geologic age. K. E. Lohman of the United States Geological Survey in Washington, D. C. has done a considerable amount of work on the Pliocene and Miocene non-marine diatomites of the United States, but most of this work is unpublished or in summary form (see Lohman, 1961).
Two of the samples studied in this paper were in direct stratigraphic association with the Yakima basalt of Miocene age in southern Wash ington (plate 52). The other samples were probably equivalent or nearly equivalent to the stratigraphic position of the diatomites in the Yakima basalt, however, some of them may be in association with the Ellensburg formation. Both the Yakima basalt and the Ellensburg formation are Miocene in age (Wilson, Keroher, and Hansen, 1959) and bear rocks of distinctly non-marine origin (Wilmarth,1937).