70 University of Washington Publications in Geology [Vol. 1 



observations made on the lithology of the rocks as well as the observations on strike 

 and dip were tied in to these traverse lines. Fossils were collected wherever 

 possible and their stratigraphic position determined. The faunal determinations 

 were made by the writer in the Paleontological laboratory of the University of 

 Washington. Twenty-five molluscan species are new and are described in the 

 report. The writer wishes to express her acknowledgments to Professor C. E. 

 Weaver, who has aided in and made possible the preparation of this report. 



HISTORICAL REVIEW 



One of the first references to the occurrence of Oligocene formations in the 

 Porter area is in a report by Dr. Ralph Arnold 1 in 1906. In this paper a small 

 geologic map of the border of the Olympic Peninsula is inserted, and upon this the 

 occurence of Oligocene-Miocene strata is indicated along the north side of Chehalis 

 River. In a paper published during the same year Dr. Arnold 2 refers to certain 

 gray shales occurring in the vicinity of Porter, Chehalis County, Washington. Men- 

 tion is made also of the occurrence of Oligocene fossils at Bean Point opposite 

 Seattle, and in northern Clallam County along the south shores of the Strait of 

 Juan de Fuca. In 1908 further reference is made to the occurrence of Oligocene 

 strata by Dr. Arnold. 3 Three new species are described from Porter which are 

 found in common with the Oligocene beds at San Lorenzo, California. These species 

 are Malletia chehalisensis, Cardium lorenzanum and Strepsidura calif ornica. In 

 the following year Dr. Arnold 4 in a paper on the Tertiary of the Pacific Coast pre- 

 sents a correlation chart in which the Porter beds are placed in the Oligocene. 



The occurrence of the Oligocene beds at Porter is considered in more detail 

 in a paper by Dr. C. E. Weaver 5 published in 1912. The beds at Porter are 

 described as being a part of the lower portion of the Blakeley formation and as 

 slightly younger than the Oligocene exposed in the region around Lincoln Creek. 

 The areal distribution of the Oligocene around Porter is indicated on a geological 

 map accompanying the report. Several new species of fossil mollusks are described 

 from this region. 



In 1913, a paper appeared entitled "The Marine Tertiary Stratigraphy of the 

 North Pacific Coast of America," by Dr. Ralph Arnold and Harold Hannibal. 6 In 

 this report the Oligocene of Washington is divided into three formations : the San 

 Lorenzo, or lowest ; the Seattle, or middle ; and the Twin River, or uppermost. These 

 three formations are grouped as the Astoria series. The marine Oligocene exposed 

 at Porter Creek is considered as belonging to the San Lorenzo or oldest division of 



1 Arnold, Ralph. Reconnaissance of the Olympic Peninsula, Geol. So<-. Am. Bull., vol. 

 17, pp. 453-454, 1906. 



- Arnold, Ralph. The Tertiary and Quaternary Pectens of California, U. S. Geological 

 Survey, P.P. No. 47, p. 15, 1906. 



3 Arnold, Ralph. Descriptions of New Cretaceous and Tertiary Fossils from the Santa 

 Cru/ Mountains, California, Proc. U. S. Nat. Museum, No. 1617, vol. 34, pp. 365-367, 190S. 



4 Arnold, Ralph. Tertiary Faunas of the Pacific Coast, Jour. Geol., vol. 17, pp. 509- 



. i . ' i . 1909. 



5 Weaver, C. E. A Preliminary Report on the Tertiary Paleontology of Western Wash- 

 ington, Wash. Geol. Survey, Bull. 15, pp. 15-16, 1912. 



Arnold, Ralph, and Hannibal, Harold. The Marine Tertiary Stratigraphy of the North 

 Pacific Coast of America, Proc. Am. Phil. Soc., vol. 52, pp. 559-604, 1913. 



