in Natural History; a genus of spars debauched by a very large admixture of earth; they are opaque, formed of thin crusts, covering vegetables and other bodies, by way of incrustations.

Of this genus we have the following species: 1. A cibdelo-grayish-white one, with a rough surface. 2. A whitish brown one; both these are friable. 3. A hard, pale-brown kind, which is the oftocolla of the shops. 4. The whitish-gray kind, with a smooth surface; this is the unicorn fossil and ceratites of authors. 5. The whitish-brown corralloid kind.