Tēs-tā'ceoŭs, a.

a. [Lat. testaceus, fr. testa, a shell; It. & Sp. testaceo, Fr. testacé. See TESTA.] Of, or pertaining to, shells; consisting of a hard shell, or having a hard, continuous shell.

Testaceous animals (Zoöl.), animals having a strong, thick, entire shell, as oysters and clams, thus distinguished from crustaceous animals, whose shells are more thin and soft, and consist of several pieces jointed, as lobsters. — Testaceous medicines or powders (Med.), preparations of shells and like substances, as the powders of crab's claws, pearl, and the like.