Thick-lipped Oyster Drill (Eupleura caudata)

SHELL LENGTH: Approximately 1 inch (2.54 cm)

This shell has a rough exterior with strong spiral lines. Many ribs run from the top to the bottom with two being larger than the others. This univalve has a large aperture with a long lower canal, a smooth inner lip, and a thick, toothed outer lip. Oyster Drills are spindle-shaped, fairly small shells growing less than two inches in length and having 9-12 ridges running from the top to bottom. These ridges are crossed by finer lines circling the shell and are usually tan or gray. The inside of the aperture is often purple. Oyster Drills predate young oysters by drilling a hole into the oyster shell and eating the soft body. Drills usually live on oyster beds, jetties, and pilings from the high tide line to about 50 feet deep where they also prey on barnacles and snails. Oyster Drills cannot tolerate low salinity; therefore, commercial oyster farmers locate their oyster beds in low salinity areas to avoid the threat of oyster drills.