‖n.; pl. L. Pennatulæ E. Pennatulas [ NL., fr. L. penna a feather. ] (Zool.) Any one of numerous species of Pennatula, Pteroides, and allied genera of Alcyonaria, having a featherlike form; a sea-pen. The zooids are situated along one edge of the side branches. [ 1913 Webster ]

‖n. pl. [ NL. See Pennatula. ] (Zool.) A division of alcyonoid corals, including the seapens and related kinds. They are able to move about by means of the hollow muscular peduncle, which also serves to support them upright in the mud. See Pennatula, and Illust. under Alcyonaria. [ 1913 Webster ]