|(Zool.)||any species of the genus Etheria, and allied genera, found in rivers of Africa and South America. They are irregular in form, and attach themselves to rocks like oysters, but they have a pearly interior, and are allied to the fresh-water mussels.|
See also: Oyster
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.