shell (e.g. electron shell)
diastrophism (movement and deformation of the earth's crust); upheaval (e.g. in politics); seismic shift; earthshaking changes
closed shell; closed shell
putamen (part of brain); frustule; silicified cell wall of a diatom
hard-shelled nut (e.g. walnut, pecan, almond)
adductor muscle (of a bivalve)
ice crust; ice rind; ice shell
Rostroconchia (class of extinct molluscs)