Pentacrinus
in zoölogy, the typical genus of the Pentacrinidæ. The column is pentagonal. P. caput medusæ is found in the Caribbean Sea; P. europæus is the larva of Antedon rosacea. In palæontology, seven species are known in the Lias, seven in the Jurassic, three in the Cretaceous, and three in the Eocene strata. Of these, P. (extracrinus) briareus, from the Lower Lias of Lyme Regis, has extraordinarily ramified arms or rays.