from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any of the extinct genus Micraster of infaunal echinoids.
from the GNU version of the Collaborative International Dictionary of English
- n. A genus of sea urchins, similar to Spatangus, abounding in the chalk formation; -- from the starlike disposal of the ambulacral furrows.
from The Century Dictionary and Cyclopedia
- n. A genus of fossil seaurchins or Echinoidea having a heart-shaped tumid test. It is very abundant in the Cretaceous rocks and occurs also in the early Tertiary.
From the genus name. (Wiktionary)