cardiacea

from The Century Dictionary.

• A suborder of Eulamellibranchiata, having the gills much folded, foot cylindric and more or less elongate, and siphons generally lacking. It contains the families Cardiidæ, Tridacnidæ, Chamidæ, and others.
• In Cuvier's system of classification, the fourth family of his testaceous acephals, approximately corresponding to the modern family Cardiidæ.
• A superfamily of bivalve mollusks, formed for the families Cardiidæ, Adacnidæ, Veniliidæ, and Glossidæ.