30 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
rated by constricted sutures, and ornamented with strong, tuberculate, 
axial ribs, of which there are 18 upon the second of the remaining whorls 
and 22 upon the penultimate turn. In addition to the axial ribs there are 
four, unequally broad, low, spiral ridges between the sutures, which are 
much wider than the spaces which separate them, the latter appearing as 
strongly incised lines. The intersections of these ridges and the ribs form 
the tubercles. The whorls slope gently from the second spiral ridge toward 
the summit, and the first row of tubercles, which is only feebly developed, 
is located on the sloping shoulder. The second set of tubercles is rounded, 
while the third and fourth rows are decidedly elongated. Periphery of the 
last turn marked by a strong smooth spiral keel, which is separated from 
the supraperipheral keel by a mere constriction. Base rather short, without 
keel, marked only by lines of growth. Aperture suboval, decidedly chan¬ 
neled anteriorly, outer lip rendered sinuous by the external sculpture; 
columella short, very broad, and slightly expanded at the insertion; a little 
lighter in color than the rest of the shell; provided with a strong callus on 
its inner edge, which is reflected over the parietal wall. Length, 4.2; 
diameter, 1.7 mm. (Bartsch.) 
Type in United States National Museum, No. 74001. Type locality, 
Monterey, California. 
Range. Monterey, California, to San Pedro. 
Subgenus Lirobittium Bartsch, 1911 
Bittium interfossa Carpenter, 1864 
Plate 75, figs. 2, 6 
Report, British Association for the Advancement of Science, 656:1864. Proceedings 
of the United States National Museum, 40:401; PI. 51, figs. 2, 6. 
With five sharp keels crossing 14 strong ribs. (Carpenter.) 
Shell rather large and robust, white, sometimes light brown. Nuclear 
whorls small, two; the first obliquely tilted, smooth; the second with two 
strong spiral cords, which divide the space between the sutures into 
three equal areas. Post-nuclear whorls appressed at the summit, strongly 
slopingly shouldered, ornamented with two strong, spiral keels, which 
divide the space between the sutures into three equal areas, and very 
strong, vertical, axial ribs, 16 of which occur upon each of the turns. The 
intersections of the axial ribs and the spiral cords form strong elongated 
tubercles, the long axes of which coincide with the spiral sculpture. These 
tubercles slope more abruptly posteriorly than anteriorly. The intersections 
of the axial ribs and the spiral cords inclose shallow squarish pits. Sutures 
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