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University of California. 



LVoi. 



specific identification, he thought he could recognize species of the 

 genera: Tapes, Cytherea, Anthdmya, Area, Macoma, Lucina, Tellina, 

 and Neverita, and that he considered the determination inconclu- 

 sive as to the age of the beds. This is the only known occur- 

 rence of this fossiliferous sandstone, and it is doubtless a mere 

 remnant of a formation which once overlaid the cherts and shales, 

 and which, therefore, can not be regarded as a constituent part of 

 this formation of the Monterey series. 



But, leaving this aside, there are numerous beds of a peculiar, 

 whitish, fine-grained sandstone, and of a gray, ocherous-weathering 

 limestone which are distinctly interbedded with the cherts and 

 shales, and which must from their persistent occurrence be regarded 

 as integral portions of the formation. 



The sandstones are usually not more than two or three feet in 

 thickness, and are chiefly noteworthy as fragmental deposits inter- 

 calated in a formation of chiefly non-clastic origin. They are 

 remarkably uniform in respect to their fine texture, the constituent 

 particles being not easily distinguished without the aid of a lens, 

 their whitish color, their mottled aspect, their highly silicious 

 character, and their limited thickness. Thus characterized they 

 are readily distinguished from almost any other sandstone of 

 common occurrence in the Coast Ranges. Their unique character 

 extends to their microscopic structure. When examined, in thin 

 section on the stage of the microscope, they are seen to be made 

 up of an aggregate of sharply-angular fragments of quartz of fairly 

 uniform size in a cement of an earthy isotropic substance similar 

 to that which makes up the bulk of certain chalky-white varieties 

 of "bituminous shale" from this and other portions of the Coast 

 Ranges. They thus differ in an essential particular from ordinary 

 silicious sandstones, and, indeed, seem to constitute a new and 

 peculiar type of fragmental silicious rocks. 



The ocherous-weathering limestones, which, equally with these 

 peculiar sandstones, characterize the formation, deserve also a 

 special note. They have a dense, compact texture, and show no 

 trace of fragmental or of organic origin, and thus differ from most 

 ordinary limestones. No fossils have ever been found in them. 

 Chemically as shown by their weathering they contain carbonate of 



