Lamellibranchiata (L. lamella, a plate; branchiæ, gills). The class of acephalous molluscs, with gills in the form of membraneous plates, of which the oyster and mussel are familiar examples.
Larva (L. larva, a mask). Applied to an insect in its first active state, which is generally different from, and, as it were, masks the ulterior form.
Ligament. A membrane close by the hinge which connects the valves.
Mantle. The external soft, contractile skin of the mollusca, which covers the viscera and a great part of the body like a cloak.
Macroura (Gr. makros, long; oura, a tail). A tribe of ten-footed crustacea (as the Lobster, Cray-fish), which have long tails.
Medusæ. A genus or family of soft radiated animals or Acalephæ, so called because their organs of motion and prehension are spread out like the snaky hair of the fabled medusa.
Molecules. Microscopic particles of matter.
Mollusc—Mollusca (L. mollis, soft). The primary division of the animal kingdom. It contains most shell-fish, slugs, &c.
Monograph (Gr. monos, one; grapho, I write). A written description of a single thing, or class of things.
Multivalve (L. multus, many; valvæ, folding doors). Shells composed of many pieces or valves, as the Chiton.