WordNet (r) 3.0 (2006):

hard-shell clam
    n 1: Atlantic coast round clams with hard shells; large clams
         usually used for chowders or other clam dishes [syn:
         quahaug, quahog, hard-shell clam, round clam]
    2: an edible American clam; the heavy shells were used as money
       by some American Indians [syn: quahog, quahaug, hard-
       shell clam, hard clam, round clam, Venus mercenaria,
       Mercenaria mercenaria]