an old term in Natural History; applied to 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 officinalis of the shops. 4. The whitish-gray kind, with a smooth surface: this is the unicornis fossil and ceratites of authors. 5. The whitish brown coralloid kind.