264 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
cusp-like tubercles, which are suddenly truncated posteriorly and slope 
gently anteriorly; the spaces between them are deep, squarish pits. Sutures 
moderately constricted, showing the peripheral cord on all the turns. Pe¬ 
riphery of the last whorl marked by a very strong spiral keel, the space 
between which and the first supraperipheral keel is almost as wide as that 
separating the supraperipheral keel from the median, and, like that, is 
crossed by the continuations of the axial ribs which extend prominently to 
the posterior termination of the peripheral keel. Base marked by a slender, 
basal fasciole which surrounds the insertion of the columella, the space be¬ 
tween the fasciole and the peripheral cord being concave. Aperture irregu¬ 
larly oval, very strongly channeled anteriorly; posterior angle obtuse ; outer 
lip thin, showing the external sculpture within, rendered decidedly sinuous 
at the edge by the external sculpture; columella short and stout, the edge 
reflected; parietal wall glazed with a thin callus. Length, 8.6; diameter, 
2.4 mm. (Bartsch.) 
Type in United States National Museum, No. 213301. Type locality, 
California. 
Range. Off San Diego, California. 
Cerithiopsis rowelli Bartsch, 1911 
Plate 70, fig. 6 
Proceedings of the United States National Museum, 40:348; PI. 40, fig. 6. 
Shell elongate-ovate, pale brownish yellow. Nuclear whorls large and 
tumid extending considerably beyond the lateral outline of the first post- 
nuclear whorl; the first half volution, smooth, well-rounded; the remain¬ 
ing one and a half decidedly inflated, strongly rounded, crossed by very 
strong acute axial ribs which are about one-third as wide as the strongly 
impressed intercostal spaces that separate them. Of these ribs, about 17 
are on the last turn. Post-nuclear whorls slopingly shouldered below the 
appressed summit marked by three tuberculate, spiral keels, which divide 
the spaces between the sutures into four equal rows. In addition to the 
spiral keels, the whorls are marked by strong, broad, axial ribs the inter¬ 
section of which with the spiral keels appear as prominent cusps. Of these 
ribs, 16 occur upon the first and second, 18 upon the third, 20 upon the 
fourth and penultimate turn. The individual tubercles of all three keels 
are truncated posteriorly and slope gently and regularly to the anterior 
border. The spaces inclosed by the axial ribs and spiral keels are well-im¬ 
pressed, squarish pits. Suture strongly constricted, periphery of the last 
whorl marked by a prominent, smooth keel; base short, almost flat, smooth, 
excepting lines of growth and a slender fasciole about the base of the 
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