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212 American Seashells
from Monterey to Lower California. A common southern species found
above high-tide mark on rocks; also on mussel beds.
Acanthina paucilirata Steams Checkered Thorn Drupe
San Pedro, California, to Lower Cahfomia.
% to /4 inch in length, characterized by about 6 spiral rows of small
squares of black-brown on a cream-white background. Early whorls cancel-
late, later whorls smoothish except for 4 or 5 very small, smooth, raised, spiral
threads. Top of whorl slightly concave. Spine at base of outer lip small and
needle-like. Aperture dentate, brownish with black squares on the outer lip.
Siphonal canal short. Common above high-tide mark in southern California.
Genus Urosalpinx Stimpson 1865
Urosalpinx cinerea Say Atlantic Oyster Drill
Figure 470
Nova Scotia to southern Florida. Introduced to San Francisco and to
England.
% to I inch in length; without varices; outer lip slightly thickened on
the inside and sometimes with 2 to 6 small, whitish teeth. Siphonal canal
moderately short and straight. With about 9 to 12 rounded, axial ribs per
whorl and with numerous, strong, spiral cords. Color grayish or yellowish
white, often with irregular, brown, spiral bands. Aperture tan to dark-brown.
This common species is very destructive to oysters. It occurs from intertidal
areas down to about 25 feet or more. Females grow faster and hence are
larger than the males. They may reach an age of 7 years. The drills move
inshore to spawn. Each female spawns once a year (May to September in
Virginia; June to September in Canada and England). The female deposits
25 to 28 leathery, vase-shaped capsules, each containing 8 to 12 eggs. U. fol-
lyensis B. Baker is an ecologic form.
Urosalpinx perrugata Conrad Gulf Oyster Drill
West coast of Florida (to Louisiana?).
Figure 47 d
Similar to cinerea, but with 6 to 9 axial ribs which are quite large at the
periphery of the whorl. The spiral cords are fewer and stronger. Aperture
rosy-brown or yellow-brown. Outer lip more thickened on the inside and
usually with 6 small, whitish teeth. This may be a subspecies of cinerea.
Common on mudflats. Always compare with Muricopsis ostreanmt Conrad
which resembles this species very closely.