274 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
by slender continuations of the axial ribs. The space immediately about 
the base of the columella is free of sculpture, excepting - fine, incremental 
lines. Aperture subquadrate, decidedly channeled anteriorly; posterior 
angle acute; outer lip rendered sinuous by the external sculpture; columella 
very broad at base, stout, somewhat twisted and curved, and the edge 
reflected. Length, 9.2; diameter, 2.6 mm. (Bartsch.) 
Type in United States National Museum, No. 14823b. Type locality, 
Neah Bay, Washington. 
Range. Vancouver Island to Monterey Bay, California. 
Cerithiopsis arnoldi Bartsch, 1911 
Plate 69, fig. 3 
Proceedings of the United States National Museum , 40:357; PI. 39, fig. 3. 
Shell elongate-conic. (Nuclear whorls decollated.) The post-nuclear 
whorls slightly rounded, ornamented by three tuberculate spiral keels of 
which one is at the summit, the anterior at some little distance above the 
suture, and the third halfway between the two. The posterior of these three 
keels is much weaker than the other two on the early turns, but gradually 
increases in size until on the last volution it is practically equal to them. 
In addition to the spiral keels, the whorls are marked by somewhat protec¬ 
tive axial ribs, which are not as strong as the spiral keels and render them 
tuberculate at their junctions. Of these ribs, 14 occur upon the first of 
the remaining turns, 16 upon the third, 18 upon the fourth, 20 upon the 
fifth, 22 upon the sixth, and 24 upon the seventh and eighth, and 26 upon 
the penultimate turn. The spaces inclosed between the ribs and spiral 
cords are strongly impressed, rounded pits. Sutures moderately con¬ 
stricted, showing the posterior edge of the first basal cord. Periphery of 
the last whorl marked by a deep sulcus, as wide as those occurring 
between the spiral cords on the spire, and, like them, crossed by the 
continuations of the axial ribs. Base very short, almost flattened, some¬ 
what concave near the columella, marked by two spiral cords of which 
the first is immediately below the peripheral sulcus, while the next, which 
is less strong, is separated from it by a narrow channel. The anterior limit 
of this cord is a mere impressed line. There is another impressed line a 
little anterior to this one. Aperture decidedly channeled anteriorly; pos¬ 
terior angle obtuse (outer lip fractured) ; columella short, stout, curved 
and slightly twisted. Length, 5.4; diameter, 1.8 mm. (Bartsch.) 
Type in United States National Museum, No. 195195. Type locality, 
San Pedro Bay, California. 
Range. Known only from type locality. 
[ 572 ] 
