152 CALIFORNIA ACADEMY OF SCIENCES [P»oc. 4th Seb. 



the Tejon Eocene of the CowHtz River, Washington. Like- 

 wise no living forms are contained in this fauna. 



The character of the sediments and the abundance of Hip- 

 ponyx ornata, Hipponyx arnoldi, Patella siibquadrata, Crepi- 

 dula, sp. and Acmcoa simplex, sessile shore forms, mark this 

 fauna as a strictly littoral one. In conclusion the fauna appears 

 to belong to a lower facies of the Molopophorus lincolnensis 

 zone of Weaver, and its distinctiveness is due in part to its 

 strictly littoral character and in part to having lived in a por- 

 tion of Oligocene time older than that of the typical Molopo- 

 phorus lincolnensis zone. 



Climatic Conditions During Lower Oligocene Time 



The presence of the genera Actceon, Conus, Epitonium, 

 Exilia, Fasciolaria, Marginella, Seraphs, Strepsidura, Bar- 

 batia and Lima mark this fauna as subtropical. This character 

 is in accord with the assignment of this fauna to the Molopo- 

 phorus lincolnensis zone, the San Lorenzo of Arnold and 

 Hannibal®, who inferentially recognized the tropical character 

 of the Lower Oligocene. Their statement concerning the 

 climatic conditions in the description of their Seattle forma- 

 tion is given as follows : "In the sections at Gettysburg, Bain- 

 bridge Island, Lincoln, Nasel River, Nehalem River, Yaquina 

 River and several other points, the San Lorenzo formation 

 is overlain conformably by a succession of beds usually finer 

 grained, thinner bedded, and more calcareous, though the ex- 

 ceptions are too numerous to mention; containing a rather 

 different fauna of less distinctly tropical type and a forerunner 

 of the boreal Twin River fauna which succeeded it." 



Weaver has shown that the Twin River formation is non- 

 existent by a careful stratigraphic survey which connects these 

 beds as one limb of a syncline with beds which Arnold and 

 Hannibal regarded as Seattle. A study of Weaver's faunal 

 zones, the Molopophorus lincolnensis zone, the Turritella por- 

 terensis zone and the Acila gettysburgensis zone, seems to 

 indicate that the upper and lower zones contain very distinctive 

 forms, but that the middle zone is transitional although more 



* Arnold, R., and Hannibal, H. The Marine Tertiary Stratigraphy of the North 

 Pacific Coast of America, Free. Amer. Phil. Soc, vol. 52, p. 582, 1913. 



