Crinoidea (“STONE-LILIES")

Echinoderms with cup shaped bodies (calices), born on a fixed, jointed stalk, attached at the aboral pole, and bearing five-branched, jointed, and pinnulate arms that are independent of the visceral cavity. a , Pentacrinus caput med usæ; b , formation of stalk after arm is cut off. The mouth and ventral surface are turned uppermost. The generative cells develop on the ventral surface of the pinnæ. All modern representatives belong to the group Neo crinoids or Articulata . Fo ils fall mostly into the group Te elata or Palæocrinoids.