What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
Any of a number of burrowing bivalve molluscs which bore into rock and other hard materials.
a clam with an oval to oblong shell (genus Hiatella, family Hiatellidae).
a mussel with a cigar shaped shell, occurring in warm seas (genus Lithophaga, family Mytilidae).