Source : Webster's Revised Unabridged Dictionary (1913)

Pholas \Pho"las\, n.; pl. {Pholades}. [NL., fr. Gr. ?, ?, a kind
   of mollusk.] (Zo["o]l.)
   Any one of numerous species of marine bivalve mollusks of the
   genus {Pholas}, or family {Pholadid[ae]}. They bore holes for
   themselves in clay, peat, and soft rocks.

Source : WordNet®

Pholas
     n : type genus of the family Pholadidae: piddocks [syn: {genus
         Pholas}]