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University of California Publications in Geology [Vol. 9 



many minor details of the hinge. It might also be mistaken for 

 8. planulata, from which it differs in being more ventricose and 

 more equilateral, besides possessing a different type of left cardinal. 



The type of this species was obtained in Puget Sound. 



Occurrence. — Recent: Alaska to San Diego, California (Dall). 

 Pleistocene: San Pedro, San Diego (Arnold). Pliocene: Etchegoin 

 (Arnold). Miocene : San Pablo ( ?) (Clark). 



Subgenus Cymbophora Gabb, 1869 



Type Mactra ashburnerii Gabb 



Hinge heavy, resilium with convex ends; right cardinal tooth 

 lacking the posterior arm; delicate, nearly at a right angle with 

 the anterior margin of the chondophore ; left cardinal slender; lat- 

 erals large and robust. 



SPISULA ASHBURNERII (Gabb) 

 Plate 26, figures 4 and 5 

 Mactra ashburnerii Gabb, Pal. Cal., vol. 1, p. 153, pi. 22, fig. 127, 1863; 

 Arnold, U. S. Geol. Surv. Bull. 396, p. 104, pi. 1, fig. 4, 1909. 



Cymbophora ashburnerii (Gabb), Pal. Cal., vol. 2, p. 181, pi. 29, fig. 

 69, 1869. 



Spisula ashburnerii (Gabb), Dall, Trans. Wagner Inst. Sci., vol. 3, pt. 4, 

 p. 879, 1898. 



This species was described by Gabb as follows : 



Shell moderate in size, subtrigonal; base broadly and regularly convex; 

 beaks central, slightly inclined forwards; posterior cardinal margin sloping, 

 straight, slightly convex; anterior faintly excavated; some specimens show 

 an umbonal angle well marked, while in others it is nearly or entirely 

 obsolete. Surface variable; specimens from some localities showing a large 

 number of regular, nearly uniform, rounded, concentric ribs; 24 while those 

 found at other places have these ribs few, entirely absent, or only repre- 

 sented by fine lines of growth. 



Hinge plate wide, chondophore spoon-shaped, shallow, with raised 

 margins ; left cardinal slender, arms of equal length, situated medi- 

 ally on the hinge plate and not overhanging the pit ; right cardinal 

 without a posterior arm, anterior one well-developed ; laterals heavy, 

 distant from the umbones ; laminae prominent, the dorsal ones 

 arising from the dorsal margin of the shell. The dimensions of the 



-* These characters were based upon specimens afterwards recognized 

 as belonging to a distinct species, 8. gabbiana. 



