the world > the earth > structure of the earth > constituent materials > earth or soil > mud > [noun] > deposited by river or sea > containing shells (4)
A fertile mud containing shells, taken from the bottom of rivers.
(See quot. 1651 and cf. snail cod, n.)
Mud containing a large number of mussels or mussel shells, used as fertilizer.
U.S. = mussel-mud, n. Obsolete.