Pro*os"tra*cum (?), n.; pl. Proostraca (#). [NL., fr. Gr. before + shell of a testacean.] Zool.

The anterior prolongation of the guard of the phragmocone of belemnites and allied fossil cephalopods, whether horny or calcareous. See Illust. of Phragmocone.

 

© Webster 1913.

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