Testacea

ANAIMONA, Aquatilia Exanguia, Bloodless Fishes, are divided into Mollia Soft Fishes without Shells; Crustata, those that are covered with thin pliant Shells; and Testacea, those which have thick, hard brittle Shells.

The echinite family […] may be deemed characteristic of the chalk formation, affording of itself as many shells as the other testacea do.

[…]to fancy, for example, that the testacea of the ocean existed first, until some of them, by gradual evolution, were improved into those inhabiting the land.