testacea noun2 •[plural only] (no longer used) Any of various shellfish, especially those of the obsolete orders Vermes or Acephala, or the suborder Thecosomata.The echinite family […] may be deemed characteristic of the chalk formation, affording of itself as many shells as the other testacea do. — 1829 •(no longer used, rare) A testaceous substance, something made of shell or shell-like material.
