Clamdog, aka the jackknife clam, is a long, smooth-shelled, burrowing clam found in the Atlantic Ocean. These clams are often collected for food. Ensis minor can grow up to 17 cm (6.7 in) in length. It is white, sometimes with reddish-brown markings. It is called the clamdog because its shape resembles that of the traditional American hot dog roll.