Definition of "half-shell" [half-shell]

• One shell of a bivalve: as, oysters served on the half-shell (that is, with the upper shell removed, and the oyster served raw on the lower one). (noun)

The Century Dictionary (Public Domain)

• "This was partly because the oysters, which arrived in Puget Sound in the 1920s, require concerted husbandry   to   produce a worthy tasting   half-shell oyster, and partly because they look a little off-putting, what with those black or brown filtering mantles around their rims."
• "Patrick McMullan Christy Turlington with Corey and Michelle Jassem Guests nibbled on treats from host Tom Colicchio's restaurants, including duck prosciutto, scallops on the half-shell, stuffed zucchini blossoms and a variety of tomatoes."
• "The experience you're paying for is the whole clam, its own half-shell stuffed with fresh, seasoned bread crumbs, then placed under a burning hot broiler so as to render it browned and just crisp enough."