stephanocrinus

from The Century Dictionary.

• noun The only genus of the crinoid family Stephanocrinidæ, an aberrant representative of the order Larviformia, in which the calyx is small and compact and consists of three basal, five radial, and five interradial plates, the radials being deeply forked, very short biserial arms arising from them. It occurs in the Silurian rocks of America and Bohemia.