Prosobranchiata 533 



feeding on clams, mussels, Crepidula, small crabs, barnacles, and even on 

 its own kind, while other investigators report the drill as perforating 

 scallops and chitons (Federighi, 1931a). Contrary to Colton's (19 10) 

 results with Sycotypus and Fulgur, the drill will feed on the meats of 

 oysters, clams, fishes, crabs, etc.* 



COLLECTING 



These gastropods are easily collected upon oyster and clam beds and 

 from wharf-piles and large boulders. Several methods may be used. 

 The following are some of the easier ways: 



The trap dredge. This dredge (Fig. 83) consists of a wire cage 

 open in front and fitted with an inclined screen. The dredge is dragged 

 over the infested oyster bed ; the oysters are picked up by the blade at 

 the edge of the dredge, moved up over the inclined plane, and the 

 drills automatically screened, falling into the cage below while the 

 oysters pass over and fall back onto the oyster bed. In this way the 

 dredge may be dragged over great areas, without involving the removal 

 of the oysters from the bottom. The most effective time for dredging is 

 after early spring when the animals have become active and are on the 

 upper layers of the oyster (Federighi, 1931a). 



The use of small concrete pillars. Small concrete pillars (Fig. 84), 

 easily handled by one man, may be set out over the bottoms. These 

 pillars, providing surfaces higher than the surrounding area of the 

 oyster beds, act as traps because the animals congregate upon them 

 owing to their tendency to creep upwards (Federighi, 1931a). After 

 3 or 4 days they are taken up, the drills removed, the pillars set out 

 again in new places. If the area is below low water mark, lines and 

 buoys may be attached to the concrete blocks, thus facilitating removal 

 and replacement. 



Wire Bag Trap. This consists of a wire mesh sac baited with young 

 oysters which is lowered over the oyster bed (Nelson, 1931). These 

 may be handled in much the same ways as the concrete pillars. 



REQUIREMENTS FOR MAINTENANCE IN THE LABORATORY 



Since Urosalpinx cinera is a marine form, it requires a laboratory with 

 running seawater. A 10-gallon tank is sufficiently large for as many 

 as 300 oyster drills, if kept clean of debris. The animals may be fed 

 on any of the various bivalves but for the best results young live 

 oysters should be used, and after these have been killed they should be 

 removed from the tank before putrefaction begins. This, during the 

 summer, is a very serious problem. 



* Editor's Note: Recent investigations by the U. S. Bureau of Fisheries show that 

 drills can be successfully fed on Carnacles and small mussels. P. S. G. 



