160 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type. Venus irns Linnaeus. 
Distribution. Europe, Pacific. 
Range in Time. Jurassic, Pleistocene. 
Venerupis lamellifera Conrad, 1837. 
Plate 39, fig. 8. 
Jour. Acad. Nat. Set., Phila 7:251; pi. 19, fig. 19. 
Shell suboval, compressed; disks with about eight lamelliform concen¬ 
tric slightly reflexed ribs, and very obscure radiating sulci; posterior 
extremity widely truncated; color white; pallial impression with a pro¬ 
found sinus. Living in holes in the rocks. (Conrad.) 
Type locality, Monterey, California. 
Range. Monterey to San Diego, California. 
Genus GEMMA Deshayes, 1853. 
Shell rounded, subtriangular, subequilateral, smooth, margins crenu- 
lated within; hinge short and narrow; three teeth in the left valve, the 
middle one conical arcuated; two divergent teeth and an intermediate pit 
in the right valve; pallial impression marginal, with a narrow deep sinus. 
(Tryon. S. S. Conch.) 
Type. Venus gemma Totten, 1834. 
Distribution. United States. 
Gemma gemma Totten, 1834. 
Amer. Jour. ScL, 26 :367; fig. 2. 
Shell small, nearly orbicular, beaks nearly central, slightly elevated; 
generally eroded. No defined lunule in front of them; surface shining, 
with minute, concentric, crowded furrows; anterior portion, and mostly 
the base, white or tinged with rose color; posterior and upper portion 
reddish purple; within white, except posteriorly, where it has the purple 
color of the outside; muscular and pallial impressions distinctly marked, 
the latter with an acute sinus; teeth divergent, the middle one in each 
valve stout and triangular, the anterior tooth of the right, and the posterior 
one of the left valve thin, and not easily distinguished; inner margin crenu- 
lated. Length, % 0 of an inch; height, % of an inch; breadth, y 1G of an 
inch. (Binney and Gould, Invert. Mass.) 
Type locality, New England. 
Range. Puget Sound to San Francisco, introduced. Also Atlantic. 
Genus PSEPHIDIA Dali, 1902. 
Shell small, vermiform, polished, with faint concentric sculpture; beaks 
not prominent; valves inequilateral, with a narrow, feebly defined lunule 
