'Micraster' definitions:

Definition of 'Micraster'

From: GCIDE

Micraster \Mi*cras"ter\, n. [NL., fr. Gr. mikro`s small + ? star.] (Paleon.) A genus of sea urchins, similar to Spatangus, abounding in the chalk formation; -- from the starlike disposal of the ambulacral furrows. [1913 Webster]