CLASS GASTROPODA 
23 
Type in United States National Museum, No. 109509. Type locality, 
Terminal Island, San Pedro. 
Range. Known only from type locality. 
Bittium subplanatum Bartsch, 1911 
Plate 77, fig. 5 
Proceedings of the United States National Museum, 40:395; PI. 57, fig. 5. 
Shell broadly elongate-conic, milk-white. Nuclear whorls a little more 
than one, well-rounded, smooth. The first of the post-nuclear whorls well- 
rounded, marked by three spiral cords, one of which is at the summit, 
another on the middle of the whorl, while a third is a little above the suture. 
The succeeding turns show four spiral cords, of which the one at summit 
is a little less strong than the rest; the remaining three divide the space 
between the sutures into four equal parts. Beginning with the fourth 
whorl, intercalated cords make their appearance between the primary 
ones, so that on the last whorl we have an intercalated cord and some¬ 
times two between all the primary cords; these, however, are never quite 
as strong as the principal ones. In addition to the spiral cords, the whorls 
are marked by decidedly curved, slender, well-rounded, almost vertical, 
axial ribs, which are scarcely indicated on the first turn, while 14 of them 
occur upon the second and third, 16 upon the fourth, 18 upon the fifth and 
sixth, 22 upon the seventh, 24 upon the eighth, and 26 upon the penultimate 
turn. The intersections of the spiral cords and axial ribs form weakly 
developed, rounded tubercles which are truncated on their posterior mar¬ 
gin, while the spaces inclosed between them are very shallow, quadrangular 
pits. Sutures strongly constricted. Periphery and base of the last whorl 
well-rounded, marked by slender, spiral cords, of which those immediately 
below the periphery are the strongest and are truncated on the posterior 
margin, sloping gently anteriorly. Of these cords, seven occur on the base 
of the type. Aperture rather large, irregularly oval, channeled anteriorly; 
posterior angle acute; outer lip thin, rendered sinuous by the external 
sculpture; columella decidedly oblique, strongly curved and reflected. 
Length, 10.9; diameter, 3.8 mm. (Bartsch.) 
Type in United States National Museum, No. 160076. Type locality, 
Catalina Island, California. 
Range. Monterey Bay south to Coronado Island, California. 
Bittium rugatum Carpenter, 1866 
Proceedings of the United States National Museum, 40:397; PI. 56, figs. 4, 5. 
Shell elongate-conic, white. Nuclear whorls a little more than one, 
well-rounded, smooth. Post-nuclear whorls appressed at the summit, de- 
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