The outer integument of a seed; the episperm, or spermoderm.

outer protective 'coat' or covering of ascidians; also, the skeleton of echinoids and other echinoderms.

a hard outer covering as of some amoebas and sea urchins

a shell or hardened outer covering. The hardened skeleton of echinoderms (Phylum Echinodermata, sea stars, sea urchins, sea cucumbers) is called a test.

many echinioderms to have fused calcite ossicles forming a rigid, external skeleton referred to as a test.

An outer covering, usually hard, secreted by some organisms