shipworm: wormlike marine bivalve that bores into wooden piers and ships by means of drill-like shells
clam: burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness
hebephrenia: a form of schizophrenia characterized by severe disintegration of personality including erratic speech and childish mannerisms and bizarre behavior; usually becomes evident during puberty; the most common diagnostic category in mental institutions