1922] Fauna from the Bocene of Washington 13 



County; {type) at locality 324, on Olequah Creek about one-eighth of a mile 

 north of Vader opposite locality 323 ;' locality 325, on Olequah Creek about 

 one-fourth of a mile north of Vader, Lewis County, Section 29, Township 11 

 North, Range 2 West. 



GENUS OSTREA UNNEAUS 



OSTREA COLUMBIANA n. Sp. 



Plate VIII, Figures 15, 16 



Description. Shell large and elongate in outline; right valve very convex 

 and irregular; left valve flat or concave with the anterior end straight dorsally, 

 swinging into the ventral margin with a broad curve which continues ventrally 

 to the posterior, ventral end; posterior end with a more or less deep concave area 

 at about one-third of the distance from the dorsal line ; shell very thick ; surface 

 of the left valve rough and irregular with overlapping laminae; surface of the 

 right valve smoother, the growth lines more regular than those of the left valve ; 

 left valve with a glossy, 'corneous outer layer over which are fine yet conspicu- 

 ous radiating lines; beaks deflected posteriorly; anterior and posterior margins 

 internally or laterally with coarse transverse grooves. 



This species is related to O. idriaensis Gabb. the left valve of O. columbiana 

 n. sp. is typically broader dorsally and less curved, and the right valve is smoother 

 and less squamose. 



The fine striae on the external corneous layer of the shell is like that 

 described and figured by Professor Harris* as occurring on Ostrea alabam- 

 iensis Lea of the Eocene of the Gulf and East Coast. 



Dimensions Co-types ; height right valve 58 mm. ; width right valve 43 mm. ; 

 thickness right valve 10 mm. ; height left valve 60 mm. ; width left valve 44 mm. ; 

 convexity left valve 30 mm. 



Occurrence. Type locality 340 (University of Washington Palaeontological 

 Collection) on Coal Creek, Cowlitz County, Section 11, Township 8 North, 

 Range 3 West; type locality 324 (University of Washington Palaeontological 

 Collection) west bank of Olequah Creek about one-eighth of a mile north of 

 Vader, Lewis County, Section 29, Township 1 1 North, Range 2 West ; locality 

 319 (University of Washington Palaeontological Collection) at McClarety ranch, 

 south bank of Stillwater Creek, one mile west of Vader, Lewis County, Section 

 30, Township 11 North, Range 2 West; locality 341 (University of Washington 

 Palaeontological Collection) on Coal Creek about two and one-half miles up 



