in natural history, the name of a genus of fossils of the class of felsen, but of the columnar, not the rhomboidal, kind. Of this genus there are only only two known species: 1. A fine kind with thin filaments and transverse filaments, found in the clayey banks of the river Nen, near Peterborough in Northamptonshire; and 2. A dull kind with thick plates and longitudinal filaments. This is not uncommon in Yorkshire, and lies sometimes in a yellow and sometimes in a blue clay.