260 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
The tubercles on the first keel are well-rounded, while those on the second 
and third are truncated posteriorly and slope gently anteriorly. Periphery 
of the last whorl marked by a deep spiral groove which is as wide as that 
separating the median from the third keel. This groove is crossed by the 
continuations of the axial ribs which stop at the anterior termination of 
the groove. Suture strongly channeled. Base moderately long, slightly 
concave, marked by a very strong spiral keel immediately anterior to the 
peripheral groove. The anterior border of this keel is limited by a slender 
incised line. A second low, weakly developd spiral cord encircles the 
middle of the base between the basal fasciole, which is a mere slender 
thread at the insertion of the columella, and the keel immediately anterior 
to the periphery. Aperture of irregular shape, decidedly channeled an¬ 
teriorly ; posterior angle obtuse; outer lip thin, rendered sinuous at the edge 
by the strong external sculpture ; inner lip decidedly flexuous, reflected over 
and adnate to the base; parietal wall covered with a moderately thick callus. 
Length, 4.2; diameter, 1.5 mm. (Bartsch.) 
Type in United States National Museum, No. 223049. Type locality, 
South Coronado Island, Lower California. 
Range. Known only from the type locality. 
Cerithiopsis charlottensis Bartsch, 1917 
Plate 67, figs. 9, 11 
Proceedings of the United States National Museum, 52:668; PI. 46, figs. 9, 11. 
Shell elongate-conic, pale brown. Nuclear whorls strongly rounded, 
three, forming a slender, very elevated spire, smooth. Post-nuclear whorls 
well-rounded, appressed at the summit, marked by rather strong, almost 
vertical, axial ribs of which 14 occur upon the first four turns, 16 upon 
the fifth, 18 upon the sixth, and 20 upon the penultimate whorl. Inter¬ 
costal spaces a little wider than the ribs. The spiral sculpture consists 
of three strong cords, of which the one at the summit is a little less strong 
than the other two. The junctions of the spiral cords and the axial ribs 
form strong tubercles; those on the cord at the summit are well-rounded, 
while those of the median cord are truncated anteriorly and posteriorly. 
The tubercles of the third cord are truncated posteriorly and sloped gently 
anteriorly. The spaces inclosed between the spiral cords and the axial ribs 
are well-rounded pits. Sutures moderately constricted. Periphery of the 
last whorl marked by a spiral groove, which equals in strength and width 
the groove that separates the median from the third cord on the spire. 
Base short, well-rounded, smooth, excepting the exceedingly fine incre¬ 
mental lines and microscopic spiral striations which are also present on 
the spire, and a very slender basal fasciole which surrounds the insertion 
of the inner lip. Aperture decidedly channeled anteriorly; posterior angle 
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