Source : Webster's Revised Unabridged Dictionary (1913)

Clypeastroid \Clyp`e*as"troid\, a. [NL. Clypeaster (L. clupeus
   shield + aster star) + -oid.] (Zo["o]l.)
   Like or related to the genus {Clupeaster}; -- applied to a
   group of flattened sea urchins, with a rosette of pores on
   the upper side.