Other shellfish included quahogs, surf clams, scallops, whelks and conchs. Examples include periwinkles, conches, and whelks. Shellfish recovered included oysters, whelks, mussels and cockles. Other commonly eaten molluscs include octopuses and squids, whelks, oysters, and scallops. On the shallow-water mud flats whelks prey on oysters, clams, and other marine bivalves. Crabs, squid, shrimp, and whelks are also caught. Experimental fisheries have included whelks, crabs and octopus. Among the most common predators on barnacles are whelks. Adult whelks are eaten by loggerhead sea turtles. On the Pacific coast of Canada, crows forage on whelks, a species of mollusk. Veined rapa whelks favor compact sandy bottoms, in which they can burrow almost completely. The shell of most knobbed whelks is dextral, meaning that it is right-handed. Rapa whelks were first found in the Black Sea in the 1940s. The aperture is usually crenulated in mature dog whelks, less often in juveniles. Additionally, vast beds of empty shells have been discovered where no living whelks are present.