Rugosa \Ru*go"sa\, n. pl. [NL. See Rugose.]

(Paleon.) An extinct tribe of fossil corals, including numerous species, many of them of large size. They are characteristic of the Paleozoic formations. The radiating septs, when present, are usually in multiples of four. See Cyathophylloid.

Source: Webster's Revised Unabridged Dictionary (1913)