quahog

An edible clam with a hard shell found along the Atlantic Coast of North America, from species Mercenaria mercenaria, formerly Venus mercenaria.

The largest size of such an edible clam, generally considered only fit for use in chowders and other clam dishes.

A similar edible clam found along coasts around the North Atlantic, generally in deeper waters, the ocean quahog, black quahog, mahogany clam or Icelandic cyprine, Arctica islandica