266 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Aperture subquadrate, posterior angle obtuse, decidedly channeled at the 
junction of the short, thick, somewhat twisted columella and outer lip. 
This description is based upon two specimens: one has the nucleus and 
11 post-nuclear whorls, and the other has furnished the description of the 
nucleus. Length of this, 7.3; diameter, 2.3 mm. (Bartsch.) 
Cotypes in United States National Museum, No. 195196. Type local¬ 
ity, Whites Point, San Pedro. 
Range. Monterey, California, to San Bartolome Bay, Lower California. 
Cerithiopsis antefilosa Bartsch, 1911 
Plate 70, fig. 9 
Proceedings of the United States National Museum, 40:349; PI. 40, fig. 9. 
Shell elongate-conic, light chestnut brown. Nuclear whorls three and 
one-half, moderately rounded, separated by a poorly defined suture; the 
first one smooth, the next two and one-half with slender, closely-spaced, 
axial threads, and fine, spiral lirations in the intercostal spaces. Post- 
nuclear whorls slightly rounded, marked by three tuberculate spiral cords 
of which the posterior one is at the summit, the anterior at some little 
distance posterior to the suture, while the third is about median between 
the two. The posterior cord is very poorly developed on the early whorls, 
in fact quite absent on the first volution, but grows steadily in size until 
in the last volution it is as strong as the other two. In addition to the spiral 
cords, the whorls are marked by vertical axial ribs which are as strong as 
the spiral cords and render the junction with them tuberculate. Of these 
ribs, 14 occur upon the first to third, 16 upon the fourth, 18 upon the fifth 
and sixth, 20 upon the seventh to ninth, 22 upon the tenth, and 24 upon 
the penultimate turn. The tubercles of the posterior cord are well-rounded, 
that of the median slightly truncated posteriorly, while on the anterior cord 
they appear truncated in the middle, sloping gently anteriorly and very 
suddenly posteriorly. Sutures strongly constricted; periphery of the last 
whorl marked by a sulcus, which is as wide as the spaces that separate 
the keels on the spire, and, like them, is crossed with the continuations of 
the axial ribs. Base short, well-rounded, marked by four spiral keels, 
which grow gradually weaker and a little closer spaced from the periphery 
to the umbilical area, the last one forming a slender basal fasciole about 
the insertion of the columella. In addition to the spiral sculpture, the base 
is marked by numerous fine incremental lines. Aperture rhomboidal; de¬ 
cidedly channeled anteriorly; posterior angle acute; outer lip thin, rendered 
wavy by the external sculpture; columella moderately long, stout, decidedly 
curved, and somewhat twisted. The type has lost the first two nuclear 
f564] 
