CLASS GASTROPODA 
255 
at the summit is almost equal to the other two. In addition to the spiral 
sculpture, the whorls are marked by vertical axial ribs which are stronger 
than the spiral cords. Of these ribs, 12 occur upon the second, 16 upon 
the third to fifth, 18 upon the sixth, and 20 upon the penultimate turn. 
The junctions of the axial ribs and spiral cords form strong tubercles, 
which are truncated posteriorly and slope gently anteriorly. The spaces 
inclosed between them are elongated, narrow pits between the first and 
second spiral cords on the early whorls, while on the last they are squarish 
pits in this region. The spaces between the median and supraperipheral 
cords are strongly impressed, large, squarish pits on all the whorls. 
Sutures strongly channeled. Periphery of the last whorl marked by a 
broad sulcus, equaling that which separates the supraperipheral from the 
median cord, crossed by the continuations of the axial ribs. Base marked 
by a strong, broad, rounded cord immediately below the periphery and a 
second less strong on its middle, while a slender thread encircles the 
insertion of the columella. In addition to this sculpture, the base is marked 
by strong, incremental lines. Aperture irregularly oval, decidedly chan¬ 
neled anteriorly; posterior angle obtuse; outer lip thin, showing the 
external sculpture within, rendered sinuous at the edge by the external 
sculpture; columella stout, curved, strongly twisted, with the edge re¬ 
flected ; parietal wall glazed with a thick callus. The type has lost the 
nucleus, eight remaining post-nuclear whorls measuring: Length, 3.4; 
diameter, 1.3 mm. (Bartsch.) 
Type in United States National Museum, No. 195182. Type locality, 
12 fathoms ofT Del Monte, Monterey, California. 
Range. Monterey Bay, California, to South Coronado Island. 
Cerithiopsis cesta Bartsch, 1911 
Plate 69, fig. 5 
Proceedings of the United States National Museum, 40:341; PI. 39, fig. 5. 
Shell elongate-conic, chestnut brown. Nuclear whorls three, well- 
rounded, and smooth, forming a slender elongate spire. Post-nuclear 
whorls strongly rounded, marked with three feebly tuberculated spiral 
keels between the sutures of which the posterior is at the summit and the 
anterior at some little distance posterior to the suture, the median one 
being a little nearer the anterior than its other neighbor. The spaces 
between these keels are not quite as wide as the keels. In addition to the 
spiral keels, the whorls are marked with feeble, somewhat irregular axial 
riblets which are less than half as strong as the spiral keels; of these ribs, 
14 occur upon the third and 32 upon the remaining whorls. These ribs 
render their junction with the spiral cords feebly nodulose. The spaces 
[ 553 ] 
