A small sketch of Cherrystone Clams from a photo on the internet. The hard clam, also known as a quahog (or quahaug), round clam, or hard-shell clam, is an edible marine bivalve mollusk that is native to the eastern shores of North America and Central America, from Prince Edward Island to the Yucatan Peninsula. Pilot Falcon fountain pen with Noodler’s Black ink and Holbein watercolors in a Stillman and Birn sketchbook.