ARCA

The name of a Linna;an genus of the Vermes Testacea, characterised by a bivalve and equivalve shell, having numerous sharp alternate teeth at the hinge. In modern systems the genus is placed among the Acephalous Lamellibranch i ate mollusca, and is raised to the rank of a family (//?-cfldi^), subdivided into the subgenera Area, Cucullaea, Pectunculus, and Nucula. [s. 84]