in natural history, the name of a genus of mollusks, of the class of the gyphums; the characters of which are, that they are of a soft texture, and of a dull opalescent look, being composed, as all the other gyphums, of irregularly arranged flat particles.

The word is derived from the Greek σάρξ, a fragment or small particle; from the flaky small particles of which these bodies are composed: of this genus there is only one known species: this is of a tolerably regular and even structure; though very coarse and harsh to the touch. It is of a very lively and beautiful red in colour; and is found in thick roundish masses, which, when broken, are to be seen composed of irregular arrangements of flat particles; and emulate a striated texture. It will neither give fire with steel, nor ferment with acids; but calcines very freely and easily, and affords a very valuable plaster of Paris, as do all the purer gyphums. It is common in Italy, and is greatly esteemed there; it is also found in some parts of England, particularly Derbyshire, but there is not much regarded.