Inarticulata

Inarticulata, the division of Brachiopoda (q.v.) in which the two valves of the shell are not united by a hinge. It includes the five small families of the Lingulidcs, Cranidcs, Bisdnidcs, Obolidce, and Trimerellidcs, of which all but the first two are extinct. The name is synonymous with Tretenterata, which is now more fashionable.