What is "thoracica"

Thoracica \Tho*rac"i*ca\, n. pl. [NL.] (Zo["o]l.) A division of cirripeds including those which have six thoracic segments, usually bearing six pairs of cirri. The common barnacles are examples.

Thoracica is a superorder of crustaceans which contains the most familiar species of barnacles found on rocky coasts, such as Semibalanus balanoides and Chthamalus stellatus. They have six well-developed limbs, and may be either stalked or sessile. The carapace is heavily calcified. The group includes free-living and commensal species.