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168 American Seashells
more than H the length of the shell. Periostracum thick, brown and with
long spicules over the region of the cords. Commonly dredged in cold,
shallow water.
Trichotropis bicarinata Sowerby Two-keeled Hairy-shell
Arctic Ocean to Alaska. Arctic Ocean to Newfoundland.
Plate 24a
I % inches in length, equally wide, with about 4 whorls. Characterized
by 2 strong, spiral carinae at the periphery, by the wide, flattened columella
and by the flaky, brown periostracum which is grossly spinose on the carinae.
Uncommon just ofl^shore in cold water.
Trichotropis insignis Middendorfl^ Gray Hairy-shell
Alaska to northern Japan.
Plate 24c
I inch in length, similar to T. bicarinata but smaller, with a much heavier
shell, weakly carinate with other numerous, uneven, spiral threads, and with
a thin, grayish periostracum. Both this species and bicarinata are easily distin-
guished from the more common cancellata by their much shorter spires and
large flaring apertures. Uncommon just offshore.
Family CAPULIDAE
Genus Capulus Montfort 18 10
Subgenus Krebsia Morch 1877
Capulus incurvatus Gmelin Incurved Cap-shell
North Carolina to southeast Florida and the West Indies.
% inch in size, cap-shaped, white to cream, and with a very large, cir-
cular to slightly oval aperture, i /4 to 2 whorls. Spire small, usually tightly
coiled, but sometimes partially free. Early whorls usually with small spiral
cords, but these are frequently worn smooth. Sculpture of small, irregular,
rounded growth lines which are crossed by numerous spiral cords which
may be rounded or sharp. Periostracum thick, light-brown, with spirally ar-
ranged rows of small tufts. Muscle scar within the aperture is horseshoe-
shaped with the swollen end just inside the columella. Uncommon on rocks
just below low water. I believe that C intortus Lamarck is merely a variant
of this species. Compare with Hipponix antiquata which is much heavier,
lacks the spiral cords and is more coarsely sculptured.
Capulus californicus Dall Californian Cap-shell
Redondo Beach to Lower California.