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University of California Publications in Geology [Vol. 8 



base of this series. They are succeeded above by thinner and more fossili- 

 ferous strata which not only contain large numbers of marine fossils but also 

 impressions of leaves and considerable fossil wood, the latter silieified and 

 lying on the surface, the rock having decomposed above it. These upper strata 

 are referred by Mr. Gabb to the Pliocene division of the Tertiary, from a 

 consideration of the number of recent species which they contain as well as 

 from their stratigraphical position. 



On the south side of Mount Diablo, Whitney also described beds 

 which are referable to the San Pablo Group. In one locality he found 

 great quantities of leaf impressions and silieified wood and at another 

 place a silieified tree stump was found "still upright — its roots in the 

 leaf-bearing stratum and its top projecting into the next above." 

 This locality is probably in the same horizon as the leaf shale of Corral 

 Hollow and Railroad Ranch, described by Turner in 1898. 



In the second volume of the Palaeontology of California, published 

 in connection with Whitney's volume on the geology of California, W. 

 M. Gabb described a number of species from the Miocene of Middle 

 California. Most of the State Survey work was of a reconnaissance 

 nature and the fossil localities were so poorly described that few of 

 them can be accurately located. Gabb did not attempt to separate 

 the faunal zones. This work has, however, been of great value to 

 later students, as is the other work of this great pioneer palaeontologist 

 of California. 



In 1863 August Remond 3 published descriptions of the following 

 species: Cardium gabbi (Pseudocardium gabbi) (Mulinia densata 

 Conrad), Ostrea bourgeoisii, Astrodapsis whitneyi, Astrodapsis 

 tumidus, Clypeaster gabbi (Scutella gabbi), and Ecliinarachnius 

 brewerianus (Scutella breweriana) . All of these, except the last, came 

 from the San Pablo in the vicinity of Kirker Pass on the north side 

 of Mount Diablo. Scutella breweriana came from a point east of the 

 town of Walnut Creek, and is one of the most characteristic forms of 

 the horizon referred to in this paper as the Scutella breweriana zone. 



In 1891 H. W. Turner 4 published a paper on the Geology of Mount 

 Diablo in which he described a section with "metamorphic" and 

 igneous rocks at the base of the column, above which came the Cre- 

 taceous (Knoxville and Chico), Eocene (Tejon), Miocene, Pliocene and 

 post-Pliocene. Turner stated that above the Knoxville there was ap- 

 parently a conformable sequence of beds. Later work in this region 

 has shown that unconformities exist at various horizons in this section. 



s Proc. Calif. Acad. Sci., vol. 3, pp. 13 and 52-54, 1863-67. 

 * Bull. Geol. Soc. Amer., vol. 2, pp. 383, 414, 1891. 



