592 ARNOLD AND HANNIBAL— MARINE TERTIARY [April 19, 



Mora. The Tertiary rocks of Tchow-un Point,'*^'' Queen Charlotte 

 Islands, represent the same horizon. 



The following fauna was obtained at Cape Blanco and Coos Bay, 

 Oregon. 



The Merced Formation (Miocene-Pliocene). 



In terming the latest Miocene or earliest Pliocene deposits of 

 the North Pacific Coast the Merced Formation, the writers recog- 

 nize the contemporaneity of the Scotia section of Eel River Valley, 

 California, the Coos Conglomerate of Coos Bay, Oregon, and the 

 Miocene-Pliocene portion of the Quinaielt formation near Taliolah, 

 Washington, with the Miocene-Pliocene beds of the Seven-mile sec- 

 tion and exposures on Twelve-mile Creek south of San Francisco, 

 California. 



As originally constituted by Lawson''" the Merced formation 

 apparently included two members, the one in question, steeply tilt- 

 ing beds extending in the Seven-mile Beach section from Mussel 

 Rock northward to the highest Scntclla bed, the other nearly hori- 

 zontal sands and clays west of Colma containing a small fauna com- 

 posed entirely of living species. Subsequently Ashley^^ utilized the 

 name ]Merced for the older portion, pointing out that the upper beds 

 should be considered separately. Recent collections made by the 

 junior writer show conclusively that the upper horizontal beds are 

 Quaternary and, though the contact is obscure, water-worn pebbles 

 containing Scntclla interlincrta Stimp. present in them indicate an 

 unconformity with the underlying ^Pliocene-Pliocene. 



Partial List of Species in the Merced Formation (Miocene-Pliocene) of the 



San Francisco Peninsula and Eel River Valley, California. 

 Pelecypoda : 



Area triliiieata Conr., 5". 



Cardium meekianum Gabb, Sj E. 



Diplodonta orbclla Gld., S.^- 



Glycymeris coalingensis Am., £."' 



Macoma calcarea Gmel., E.^- 



49a Dawson, G. M.. Rept. Geol. Sur. Can., 17SS-9 (18S0), p. 875, calls this 

 Skonum Point. Dr. C. F. Newcombe informs the writer that Tchow-un is 

 more correct. 



50 Bull. Dept. Geol. Univ. Cal., I., 1S94, p. 115-160. 



5^ Jour. Geol, III., 1895, p. 441-6. 



