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}.
[1913 Webster]