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 



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. 



