GLOSSARY. 107 
umbones are cardinal, or primary ; those on either side, 
lateral, or secondary teeth. 
Ineurved. Bent, or turned inward. 
Inequilateral. Having the sides unequal. 
Inequivalve. Having unequal valves. 
Involute. Rolled inward. 
Jaw. See Buccal plate. 
Labia. Lips. The border of the aperture of univalves. The 
inner lip (columella) may be curved, horizontal, oblique, 
plaited, or straight. The outer lip may be acute, alated, 
digitated. 
Ligament. ‘The transverse fibres which tie the two valves 
together. They are generally just behind the umbones. 
Limb. The margin of bivalve shells. 
Lingual ribbon. See Tongue. Also page 17. 
Longitudinal. Lengthwise. In univalves, from the apex ; in 
bivalves, from the umbo to the base. 
Mantle. An external thick skin which envelops the bodies 
of mollusks. 
Margined. With a thickened, or colored border. 
Microscopic. Very small. Not easily seen without a glass. 
Molluscous. Soft. Hence Mollusks, soft animals. 
Muscular impressions. ‘The scars on the inside of bivalves, 
caused by the insertion of the adductor muscles. They 
are single in the oyster ; two, in the unio, etc. 
Nacre. The pearly substance of which some shells are formed. 
It lines the shell of the Unionide. 
Nodose. Knotty. 
Ochreous. Color of yellow ochre. 
Olivaceous. A greenish olive color. 
Opaque. Impervious to light. 
Operculum. A horny scale, or bony plate, attached to the 
foot of many mollusks, which, when the body is drawn in, 
closes the shell, like a door. 
Ovate. Egg-shaped. 
Ovoid. Egg-shaped. 
Papillate. Covered with dots, or pimples. 
Patulous, Open, gaping. 
