154 PBOCEEDrS-GS OF THE PACIFIC COAST SECTION 



another. The faunas do vary somewhat from top to bottom of the entire 

 series, but the variation depends on shallow or deep water deiDosits. The pres- 

 ence of the genus Aturia has been used as an indicator of the Oligocene at 

 Astoria, but rec-ent investigations show its occurrence throughout the entire 

 Lower Miocene series. It would t>e difficult to apply the term Oligocene to 

 any part of the Lower Mioc-eue in Washington, and. using the same criteria, 

 not apply it to the Lower Miocene series, including everything below the dis- 

 tinctively Upper Miocene, which here roughly is to be correlated with the 

 San Pablo. 



FAUX A OF THE OLIGOCENE (f) OF OREGOX 

 BY F. M. A2n)ERS0X 



( Abstract) 



An account of the stratigraphic and faunal relations of the Middle Tertiary 

 at Pittsburg and Astoria, Oregon. The beds are conformable and Lower 

 Miocene in age. 



Discussioir 



Mr. Haxxibal stated that an unconformity exists at Astoria, and that the 

 Sooke beds, which are equivalent to or younger than the Astoria shales, c-on- 

 tain no living spec-ies and are Oligocene in age. 



Mr. AxDEBSOx stated in reply that he had studied the beds at Astoria, but 

 no difference in dip or strike can be found. 



FAUXAL ZOXES OF TEE MARTIXEZ EOCEXE OF CALIFORXIA 

 BY BOY E. DICKEBSOX 



(Abstract) 



Three major faunal zones are recognized in the Martinez Group. The lower- 

 most of these zones is characteristically developed in the Martinez area. 4 

 miles north of Mount Diablo, in the basal beds of this group. A middle zone 

 is well developed in this area, as well as at the type locality. This middle 

 zone is characterized by Trochocyathus zitteli (Merriam) and several other 

 species, which do not range downward to the basal portions nor upward in 

 the Solen staiitoni or uppermost zone. The upr>ermost zone is marked by the 

 abundance of Solen stantoni Weaver, by the absence of many species of the 

 Trochocyath us zitteli zone, and by the presence of a few species which do not 

 oc-cur in the middle or basal jwrtions of this group. 



COilPARISOX OF THE OYSTERS OF THE LOWER AXD UPPER HORIZOXS OF 

 THE M IOC EXE OF THE IIUIR SYXCLIXE 



BY WILLIAM V. CBrZSS 



(Abstract) 



The large Mioc-ene oysters have been called Ostrea titan indiscriminately, 

 principally on external appearanc-e. A careful study of the muscle impressions 

 and the ligamental pits indicate that two or three species are present in the 

 beds of the Monterey series at Muir Station, California. 



