THE TERTIARY AND QUATERNARY PECTEN8 OF CALIFORNIA. 



Bv Kali'h Aknold. 



IT^TRODUOTIOX. 



This paper consists of two parts. The first is a brief outline of the ditiereut 

 Tertiary and Pleistocene formations of California, giving the type localities, where, 

 when, and by whom first described, their salient characters, where the}' and their 

 supposed equivalents are known to occur, the species of Pecten found in them, 

 and their tj'pical fauna as far as known. The second is devoted to the description 

 and illustration of all of the known Tertiary, Pleistocene, and Recent Pectens of 

 the western coast of North America from Alaska to and including the Gulf of 

 California. With the description of each species is also given an account of its 

 geologic and geographic range and, where practicable, its associated fauna. 



This particular genus was chosen for study because of its great \-alue for the 

 stratigraphic determination of the Tertiary formations of the west coast and 

 because of the large amount of material available at the time the work was 

 undertaken. The genus is admirably adapted to purposes of correlation because 

 of {a) its occurrence in every important Tertiary horizon in California, {h) the 

 limited vertical and wide geographic range of most of its species, and {<:) the 

 comparatively simple yet salient characters which niark the different species. 



The present paper is a larger and more comprehensive one than was contem- 

 plated when the work was first begun. The original plan was simply to monograph 

 onl\' the fossil Pectens of California, but as the work progressed it soon became 

 apparent that the original subject could ))e thoroughly treated only by a more 

 or less detailed consideration of the fossil Pectens of the adjacent territory and 

 the living members of the genus found along the whole western coast of North 

 America. To give the paper its greatest possible value, it became necessary to 

 define as accurately as possible the stratigraphic and geographic range of each 

 species; and in order to do this consistently an examination of all of the available 

 marine Tertiary paleontologic material from the west coast was undertaken. Then, 

 that the data thus obtained might be made more available and that the relations 

 of the different faunas and horizons of the California Tertiary might be the more 

 clearly .set forth, it was deemed advisable to include a brief outline of the char- 

 acteristics, geographic range, and faunas of the different Tertiary formations. 



It was obvious that any scheme of classification of the Pectin ida^ based wholly 

 upon specimens from the Pacific coast would necessarily be disconnected and unsat- 

 isfactory. It seemed advisable, therefore, to adopt some system which was founded 



