Source : Webster's Revised Unabridged Dictionary (1913)

Pectostraca \Pec*tos"tra*ca\, n. pl. [NL., fr. Gr. ? fixed + ?
   shell of a testacean.] (Zo["o]l.)
   A degenerate order of Crustacea, including the Rhizocephala
   and Cirripedia.