CLASS GASTROPODA 
277 
than that separating the peripheral cord from the first supraperipheral. 
Aperture subquadrate, decidedly channeled anteriorly; posterior angle 
obtuse; outer lip rendered wavy by the external sculpture; inner lip 
sigmoid. 
Type in United States National Museum, No. 363785, comes from 
Santa Cruz, California. It has 10 whorls and measures, length, 5.9 mm.; 
diameter, 2 mm. 
Genus SEILA A. Adams, 1861 
Shell with simple spiral ribs. (Tryon, Manual of Conchology.) 
Type. Cerithiopsis dextroversa Adams and Reeve. 
Distribution. California to Panama, West Africa, China, Australia, 
Atlantic to West Indies, Scotland, Norway, Gulf of St. Lawrence, 
Mediterranean. 
Seila montereyensis Bartsch, 1907 
Proceedings of the United States National Museum , 33:177. Also 40: PI. 41, fig. 5. 
Shell large, robust, brown. (Extreme apex lost in all our specimens.) 
One of the cotypes has two and a half nuclear whorls remaining. These 
are rather inflated, evenly rounded, marked by many slender, obliquely 
retractive, axial riblets. The transition of the nuclear sculpture to the post- 
nuclear is very abrupt. The sculpture of the post-nuclear turn consists of 
three very strong, equal, and equally spaced lamellar spiral keels between 
the sutures. Channels separating the spiral keels well-rounded, a little 
wider than the keels, crossed by many subequal and subequally spaced 
slender riblets, of which about 40-50 appear on the whorls. Periphery of 
the last whorl marked by a fourth spiral keel not quite as strong as the 
keels of the spire and a little more closely placed to the keel posterior to it 
than that is to its neighbor above it. Base marked by a spiral keel which 
equals the peripheral keel in strength, separated from it by a channel a 
little narrower than the supraperipheral groove. Both of these channels 
are crossed by the axial riblets. The remaining portion of the base slopes 
somewhat concavely toward the stout columella. Under the microscope the 
entire surface of the spire and base appears marked by fine lines of growth 
and spiral striations. Aperture subquadrate, decidedly channeled an¬ 
teriorly ; outer lip rendered sinuous by the spiral keels, parietal wall and 
edge of columella covered by a moderately strong callus. The nuclear 
structures were described from a young specimen. Length, 3.6; diameter, 
1.4 mm. The type has 10 whorls (the first two nuclear whorls probably 
being lost). (Bartsch.) 
Cotype in United States National Museum, No. 195206. lype local¬ 
ity, Monterey, California. 
Range. Monterey, California, to Todos Santos Bay, Lower California. 
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