Micraster n. (Paleon.) A genus of sea urchins, similar to Spatangus, abounding in the chalk formation; from the starlike disposal of the ambulacral furrows.
... beings offers a similar testimony to that already alluded to. If there is a type of Echinoderms characteristic of a geological period, it is the genus Micraster of the cretaceous formation, in its original circumscription. No species of this genus is known to have existed during the Tertiary era, and no living species has as yet been made known. You may therefore imagine my surprise when the ... — Louis Agassiz: His Life and Correspondence • Louis Agassiz
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