Washington, DC: United States Geological Survey/USGS/Government Printing Office/GPO, 1973. Softcover. Item #47162
Marine mollusks from the basal shale (Cymric Shale Member) and the overlying sandsone (Wygal Sandstone Member) are of provincial Oligocene age. Warm-water assemblages from the Wygal Sandstone Member represent a previously unrecognized biostratigraphic unit of late Oligocene age in California. 48 pages with maps, tables, systematic descriptions, references and index, plus the nine photographic plates bound in the rear. Bound in original gray stiff paper covers printed in black. Signature of geologist J. Wyatt Durham on the front cover. An area of light orange offsetting on the front cover. A near fine copy.