mollusc

‖prop. n. pl. [ NL. See Mollusk. ] (Zool.) One of the grand divisions of the animal kingdom, a phylum including the classes Cephalopoda, Gastropoda, Pteropoda, Scaphopoda, and Pelecyopoda (syn. Bivalvia, formerly called Lamellibranchiata, or Conchifera). These animals have an unsegmented bilateral body, with most of the organs and parts paired, but not repeated longitudinally. Most of them develop a mantle, which incloses either a branchial or a pulmonary cavity. They are generally more or less covered and protected by a calcareous shell, which may be univalve, bivalve, or multivalve. [ 1913 Webster +PJC ]

☞ Formerly the Brachiopoda, Bryzoa, and Tunicata were united with the Lamellibranchiata in an artificial group called Acephala, which was also included under Mollusca. See Molluscoidea. [ 1913 Webster ]

a. (Zool.) Of or pertaining to mollusks. -- n. A mollusk; one of the Mollusca. [ 1913 Webster ]

a. [ Mollusca + -oid. ] (Zool.) Resembling the true mollusks; belonging to the Molluscoidea. -- n. One of the Molluscoidea. [ 1913 Webster ]

a. (Zool.) Molluscoid. [ 1913 Webster ]

‖n. pl. [ NL. See Mollusk, and -oid. ] (Zool.) A division of Invertebrata which includes the classes Brachiopoda and Bryozoa; -- called also Anthoid Mollusca. [ 1913 Webster ]

☞ Originally the Tunicata were included under Molluscoidea, from which they are known to differ widely in structure and embryology. Molluscoidea were formerly considered a subdivision of Mollusca, but they are now known to have more relationship with Annelida than with Mollusca. [ 1913 Webster ]

a. (Zool.) Molluscan. [ 1913 Webster ]