44 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Acila gettysburgensis zone Upper Oligocene 



Turritella porterensis zone Middle Oligocene 



Molopophorus lincolnensis zone Lower Oligocene 



The strata in which these zones are contained are referred 

 to in this paper as horizons, the term being used in the sense 

 of a deposit formed during a certain time and identified by 

 certain distinctive fossils. 



The type locality for the Molopophorus lincolnensis zone 

 occurs along the south bank of Chehalis River near the mouth 

 of Lincoln Creek. This fauna possesses many characteristics 

 in common with the underlying Tejon Eocene, but more with 

 the Turritella porterensis zone above. The strata character- 

 ized by this fauna may be referred to as the Lincoln horizon.* 



The Turritella porterensis zone is to be found well repre- 

 sented in the sandstone blufifs along the north bank of Che- 

 halis River near the junction of Porter Creek. The sediments 

 containing this fauna have been referred to as the Porter 

 horizon. Among the more characteristic fossils occurring in 

 this fauna are Phacoides acutilincatus (Conrad), Thyasira bi- 

 secta (Conrad), Thracia trapesoidea Conrad, Cardium loren- 

 sanum (Arnold), Turritella porterensis Weaver, Drillia stan- 

 fordensis (Arnold) and Malletia chehalisensis Arnold. It is 

 possible that the upper portion of this zone may be represented 

 in the extreme lower portion of the section at Orchard Point. 



The type section of the third or Acila gettysburgensis zone 

 occurs within the strata exposed near the entrance to the Brem- 

 erton Navy Yard. Most of the faunas from the post-Tejon 

 and pre-glacial strata in the Puget Sound basin belong to this 

 zone. The sandstones and shales containing the fauna form 

 the Blakeley horizon. 



The fourth division, or Area montereyana zone, is to be 

 found in the sandstones outcropping along Alockaman River 

 in Wahkiakum County, 12 miles north of Cathlamet. It also 

 occurs in the sandstone and shale exposures along the south 



*There is considerable doubt in the writer's mind as to the wisdom of using the 

 term, horizon. In geological literature it is often used in a very loose sense. Suf- 

 ficient geological field evidence is not available to warrant the term formation as yet. 

 Without the introduction of an entirely new word to express the idea of an assem- 

 blage of varying types of rocks all of which are characterized by the same distinctive 

 fauna, it becomes necessary to choose one which has been used most nearly in such a 

 sense. 



