272 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
ribs, of which 16 occur upon the first to fifth, 18 upon the sixth, 20 upon 
the seventh, and 24 upon the last turn. Intercostal spaces about two-thirds 
as wide as the ribs. In addition to the axial ribs there are three strong 
spiral cords, of which the first is about as far anterior to the summit of 
the whorls as it is distant from the median neighbor. The first of these 
spiral cords is a little less strongly developed on the earlier whorls than 
on the succeeding turns, where it almost equals the other two. The junc¬ 
tion of the axial ribs and spiral cords forms strong tubercles, of which 
those on the cord are truncated posteriorly and slope gently anteriorly. 
The same is true of the suprasutural cord. On the last whorl, however, 
the tubercles are more elongated and the truncation at the anterior margin 
is less pronounced, the long axis of the tubercles coinciding with the axis 
of the shell. The spaces inclosed between the axial ribs and spiral cords 
are well-rounded pits. The summit of the whorl falls a little anterior to 
the peripheral cord, and lets this appear as a narrow, smooth, sinuous 
thread in the somewhat constricted suture. Periphery of the last whorl 
marked by a strong cord, which constitutes the termination of the axial 
ribs. Base short and rounded, but concave at the junction with the 
columella. The junction of the columella and the base is marked by a 
slender spiral cord. Aperture broadly oval, decidedly channeled anteriorly ; 
posterior angle obtuse; outer lip thin, rendered sinuous by the external 
sculpture, which is also seen within the aperture by transmitted light; 
inner lip reflected over and appressed to the columella. Length, 7.5; 
diameter, 2.5 mm. (Bartsch.) 
Type in United States National Museum, No. 268746. Type locality, 
Forrester Island, Alaska. 
Range. Forrester Island, Alaska, to Puget Sound. 
Cerithiopsis signa Bartsch, 1921 
Proceedings of the Biological Society of Washington, 34:36. 
Shell elongate-conic, pale brown. First half post-nuclear whorl smooth, 
the next one and a half well-rounded and marked by rather distantly 
spaced, almost vertical axial ribs. Post-nuclear whorls appressed at the 
summit, marked by strong, rounded, almost vertical axial ribs, of which 
18 occur upon the first, 14 upon the second to sixth, 16 upon the seventh, 
and 18 upon the last turn. The spiral sculpture consists of three strong, 
equally spaced cords, which are crossed by strong axial ribs. The inter¬ 
sections of the axial ribs and the spiral cords form strong tubercles, which 
are truncated on their posterior margin, and slope gently anteriorly in all 
three groups. The spaces inclosed between the cords and the ribs are 
elongated pits, which have their long axis coinciding with the spiral 
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