micraster definition

  • noun:
    • Any of the extinct genus Micraster of infaunal echinoids.
    • A genus of ocean urchins, just like Spatangus, abounding within the chalk formation; -- through the starlike disposal regarding the ambulacral furrows.
    • A genus of fossil seaurchins or Echinoidea having a heart-shaped tumid test. It is extremely abundant in the Cretaceous rocks and occurs in addition in the early Tertiary.
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