216 MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
carinate internally, smooth, narrow and small. Aperture rhomboidal, 
pearly, with grooves answering to the exterior ribs. Columella straight, 
with a slight callosity, but not reflected. Min. diam., 3; maj. diam. 4; 
alt., 4 inch. 
Type in United States National Museum. Type locality, Monterey, 
California. 
Range. Monterey to San Diego, California. Fossil: Pleistocene. 
Family VITRINELLIDAE 
Genus VITRINELLA C. B. Adams, 1850 
Shell turbiniform, vitreous, minute, with a large, orbicular, aperture; 
either umbilicated, or with the umbilical region deeply and widely indented. 
(C. B. Adams.) 
Type ? 
Distribution. West Indies, Panama, and west coast North America. 
Vitrinella williamsoni Dali, 1892 
Plate 106, figs. 4, 6 
Proceedings of the United States National Museum, 15:202; PI. 21, figs. 2, 3. 
Shell small, white, depressed, with two and a half whorls; spire flat¬ 
tened; suture appressed with a shallow channel or excavation outside of 
the appressed margin of the whorl, outside of which the convexity of the 
whorl rises higher than the suture. Base slightly more rounded than the 
upper side, with a wide and flaring umbilicus; periphery rounded; aperture 
rounded, oblique; surface polished, finely striate here and there by the 
incremental lines which are most prominent above. Maximum diameter of 
shell, 5.5; minimum diameter, 4.5; altitude, 1.25 mm. (Dali.) 
Type in United States National Museum, No. 106856. Type locality, 
San Pedro, California. 
Range. Known only from type locality. Fossil: Pleistocene, San 
Pedro, California. 
Vitrinella oldroydi Bartsch, 1907 
Plate 107, figs. 1, 2, 3 
Proceedings of the United States National Museum, 32:167, figs. 2, 3. 
Shell small, sublenticular, semitransparent, a little more convex above 
than below. Nepionic whorls not differentiated from the rest, the entire 
upper surface smooth and shining, marked only by irregularly distributed 
[8181 
