168 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
striate; aperture large, oblique, deflexed above. Alt., 4; diam., 5 mm. 
(Tryon and Pilsbry, Manual of Conchology .) 
Type in Cooper Collection, No. 1056. Type locality, Catalina Island. 
Range. Puget Sound to San Martin Island, Lower California. 
Leptothyra paucicostata Dali, 1871 
American Journal of Conchology, 7:131. 
Shell small, depressed, rounded, of three whorls. Sculpture consisting 
of seven revolving strong ridges, with the interstices deeply channeled, and 
marked by evident lines of growth. In a few specimens these are thickened 
at regular intervals, forming faint transverse riblets, which do not reach 
as high as, or pass over, the revolving ribs. Suture deep, channeled. 
Apical whorl smooth, translucent, the others solid and strong. Aperture 
rounded, peristome thickened, continuous with an internal groove for the 
operculum. Columella ending in a toothlike knob or callosity, which is 
especially sharp and prominent in young shells. Throat pearly white. 
Operculum of a few whorls, smooth, externally concave with thickened 
edges; circular, calcareous. Color of shell usually of a rusty brown, on 
the ribs alternating darker and lighter in spots, or reddish, in a similar 
way, or pure white. Interspaces usually light, but sometimes of the same 
color as the ribs. Alt., .12; lat., .2 in. (Dali.) 
Type in United States National Museum. Type locality, Monterey, 
California. 
Range. Monterey to Coronado Islands. 
Leptothyra paucicostata fenestrata Bartsch, 1919 
Proceedings of the United States National Muse\im, 56:358. 
Shell in which, under the strong spiral sculpture, there is visible in the 
interspaces a certain number of raised radial threads forming more or less 
evident reticulation. (Bartsch.) 
Type in United States National Museum. Type locality, Tia Juana, 
Lower California. 
Range. Monterey to Coronado Islands. 
Leptothyra juanensis Dali, 1919 
Proceedings of the United States National Museum, 56:358. 
Shell solid, turbinate, very dark olive, with a very minute smooth 
nucleus and about five well-rounded whorls; suture obscure, not appressed; 
spiral sculpture of (on the penultimate whorl five, on the last whorl about 
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