NEW AND CHARACTERISTIC SPECIES OF FOSSIL MOL LUSKS FROM THE OIL-BEARING TERTIARY FORMA-TIONS OF SOUTHERN CALIFORNIA. By Ralph Arnold, Paleontologist, U. S. Geological Survey. INTRODUCTION. Among the fossils commonly found in or characteristic of certain of the oil-bearing Tertiary formations of southern California are the species and varieties mentioned in the following pages. The new forms are described and figured; those previousl}" described are simply figured, but a brief note concerning their occurrence is inserted in the explanation accompanying each drawing. It has been deemed advis-able to insert figures of the old species in this paper because the descrip-tions and illustrations of these forms are in publications inaccessible to most readers, and it is essential for the proper identification of the faunas that certain of the old species be known. The difi^erentiation of the various geologic formations in the southern coast ranges of Cali-fornia depends almost entirely upon their palentology, so that it has been the aim of the writer to give in this paper those species and only those which will aid in the determination of the horizon of the various faunas found in that region. These fossils, together with some others, will be figured on Plates XXV to XLI, Bulletin No. 309, U. S. Geo-logical Survey. The following new species and varieties are found in the yellow sandstone of the lower Miocene at the head of Topauga Canyon, 3 miles south of Calabasas, Los Angeles County, California. LIST OF LOWER MIOCENE FOSSILS FROM TOPANGA CANYON. Myiilus mathevsonii Gabb var. e.vpaiisn><, new variety. Cerithium topangensis, new species. Chlorostoma dalli, new species. Bathytoma keepi, new species. Macron merriami, new species. Ocinebra toimngensis, new species. Purpura edmondi, new species. Sigaretus perrini, new species. Turbo topangensis, new species. Proceedings U. S. National Museum, Vol. XXXII— No. 1545. 525
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