Linguiformed, tongue-shaped. Lip, the outer edge of the aperture of univalves. Lobated, rounded at the edges. Longitudinal, the length of the shell. Lunated, formed like a half moon. Lunule, crescent-like. Luniform, shape of a crescent. M. Margin, the whole circumference or outline of the shell in bivalves. Marginated, having a prominent margin or border. Membrane, a web of fibres. Mouth, see Aperture. Muscular impressions, marks made by the animal in adhering to the shell. Mottled, clouded or spotted. Mucronate, ending in a sharp point. Multilocular, many chambered. Muricated, clothed with sharp spines. N. Nacred, pearly. Nemoral, belonging to a wood. Nited, glossy. Nodose, knotty. Nucleus, a kernel. O. Obsolete, obliterated. Oblong, oval. Ocellated, eye-like spots. Ochreous, colour of yellow ochre. Offuscated, darkened, clouded. Olivaceous, of a greenish olive colour. Operculum, which closes the aperture of the shell. Orbicular, circular, round. Orifice, an opening or perforation. Ovate, shaped like an egg. Ovoid, oval. P. Papillose, pimple, dotted. Papyraceous, thin as paper. Patulous, with a gap or opening. Partitions, processes dividing the shells of the Nautilus, Serpula, &c. Pectinated, resembling the teeth of a comb. Pedicle, the support of the Anatifera and its corresponding species. Peduncle, a tube on which any thing is seated. Pellucid, transparent, clear, bright. Pentagonal, having five sides. Perforated, pierced with holes. Pervious, admitting passage. Pillar, in univalves the internal continuation of the columella or inner lips, extending from the _base_ to the _apex_. Pinnated, winged. Plaited, folded. Plaits, folds. Plicated, folded or plaited. Posterior, see Margin. Produced, lengthened out. Protrude, to thrust forward. Punctuated, like the punctures of a thimble. Pyriform, pear-shaped. Q. Quadrangular, having four right angles. Quadruplicated, having four plaits. R. Radiated, furnished with rays. Radicated, fixed by the base to another body. Rectangular, having right angles. Recurvated, turned backward. Recurved, bowed back. Reflected, bent backward. Refracted, abruptly bent. Reniform, kidney-shaped. Replicated, folded or plaited. Reticulated, formed like a piece of net-work. Retuse, ending in an obtuse sinus. Reversed spire, see Heterostrophe. Revolute, rolled backward. Ribbed, having longitudinal ribs. Ridge, the upper part of a slope. Rostrum, the beak. Rugose, wrinkled. S. Sanguinaceous, divided into chambers.