\Pro*["o]s"tra*cum\, n.; pl. {Pro["o]straca}. [NL.,
fr. Gr. ? before + ? shell of a testacean.] (Zo["o]l.)
The anterior prolongation of the guard of the phragmocone of
belemnites and allied fossil cephalopods, whether horny or
calcareous. See Illust. of {Phragmocone}.