36 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
parietal wall covered with a thick callus. Length, 13.3; diameter, 3.8 mm. 
(Bartsch.) 
Type in United States National Museum, No. 196209. Type locality, 
Lower California, in drift. 
Range. Destruction Island, Washington, to Lower California. 
Bittium fetellum Bartsch, 1911 
Plate 75, fig. 4 
Proceedings of the United States National Museum, 40:409; PI. 51, fig. 4. 
Shell moderately large, elongate-conic, light yellow. (Nuclear whorls 
decollated in all our specimens.) Post-nuclear whorls well-rounded, slightly 
shouldered at the summit, marked by three, slender, spiral keels, which 
divide the space between the sutures into four equal areas. (In addition to 
the three spiral keels, there is a tendency in many of the specimens to have 
feeble, intercalated cords between the stronger ones.) The axial sculpture 
consists of decidedly curved, slender ribs, of which 20 occur upon the 
fourth post-nuclear whorl in the type, 22 upon the fifth, and about 36 upon 
the penultimate turn. The spaces inclosed between the ribs and the spiral 
cords are large, shallow, squarish pits on all the turns but the last; on this 
they are much longer than broad, their long axes coinciding with the axial 
sculpture. The intersections of the ribs and spiral cords form slender, 
sharp cusps. Sutures strongly constricted. Base of the last whorl mod¬ 
erately long, slightly curved, marked by four spiral cords, of which the 
two middle ones are equal and stronger than the others. Entire surface of 
spire and base-marked by numerous strong lines of growth. Aperture 
large, channeled anteriorly; posterior angle obtuse; outer lip thin, rendered 
sinuous by the external sculpture; columella very oblique, curved, and 
reflected; parietal wall glazed with a thick callus. Length, 9.3; diameter, 
3.5 mm. (Bartsch.) 
Type in United States National Museum, No. 198617. Type locality, 
off Catalina Island in 6 fathoms. 
Range. Known only from type locality. 
Genus POTAMIDES Brongniart, 1810 
Shell turriculated, whorls angulated and coronated; aperture prolonged 
in front into a nearly straight canal; outer lip thin, sinuous; epidermis 
thick, olive brown. Operculum many-whorled. (Tryon, Structural and 
Systematic Conchology .) 
Type. Potomides lamarckii Brongniart. 
Distribution. California, Africa, India. In the mud of the Indus 
they are mixed with species of Ampullaria. Fossil, Eocene. 
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