in natural history, a genus of spars debafted 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 greyish-white one, with a rough surface. 2. A whitish brown one: both these are friable. 3. A hard, pale-brown kind, which is the otecolla of the shops. 4. The whitish-grey kind, with a smooth surface: this is the unicorn fossil and ceratites of authors. 5. The whitish-brown coralloide kind.