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212 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 Figure 47 d West coast of Florida (to Louisiana?). 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.