Geological Papers. 175 



Shell small, subovate to trigonal and subrhomboidal, convex, of 

 medium thickness; beaks posterior to center, turned posteriorly: 

 posterior end short, obliquely truncated ; anterior end long, rounded ; 

 surface marked by divaricating striae; binge with numerous sharp 

 teeth on each side and with prominent internal cartilage-pit. 



This is a very variable species; its rangQ covers the entire Ter- 

 tiary series represented in this region, though it is rare in the Oli- 

 gocene-Miocene formation along the Strait of Fuca. It is very 

 abundant in the Quillayute Pliocene. Specimen figured is from 

 the Quillayute formation.^* 



Living: Sitka to San Diego (Cooper); Puget Sound; Quilla- 

 yute Bay (Reagan). 



Pleistocene: San Pedro (Arnold); San Diego to Santa Barbara 

 ■ (Cooper; Gabb). 



Pliocene: San Fernando (Grabb; Cooper); San Diego well 

 (Cooper); San Pedro, Cal. (Arnold); Quillayute, Wash. (Rea- 

 gan). 



Miocene: Astoria, Ore. (Conrad; Cooper; Gabb); Martinez; 

 Griswold's, San Benito county, California (Cooper). 



Oligocene-Miocene: Blakely, near Seattle, Wash. (Arnold): 

 Gettysburg, East Clallam, Wash. (Reagan). 



3. Nucula {Acila) gettysburgensis n. s. Plate I, fig. 3. 



Shell resembling ]V. (Acila) casti^ensis Hds. but much larger. 

 Shell trigonal, convex, medium thickness; umbones considerably 

 posterior to center, turned posteriorly, posterior end 16, anterior 

 extremity 24.5 from umbones; posterior end short, truncated, con- 

 cave back of umbones; anterior end rounded to arcuate, forming 

 an acute angle with the anterior extremity; ventral and cardinal 

 margins subparallel; lunule area large, slightly scooped out, sculp- 

 tured same as rest of shell; a low ridge fronts each valve back of 

 the lunule area, back of which there is a wide, flat, curved sinus 

 extending from the umbo to the ventral margin, widening as it 

 approaches that margin; surface divaricately sculptured, also orna- 

 mented with about seven concentric low ridges; inside of shell not 

 seen. 



Dimensions: Lat., 28; alt., 19.5. 



The shell figured is from the Gettysburg formation. 



This shell is easily distinguishable from N. castrensis Hds. by 

 its larger size, more truncated, concave posterior extremity, large 

 lunule, and by its umbones being placed more posteriorly; and 



34. The specimens obtained from East Clallam possess a finer surface sculpture than those 

 of the Quillayute formation. 



