386 THE CHICAGO ACADEMY OF SCIENCES. 
Lanceolate. Gradually tapering to a point (pl. xxxii, fig. 3). 
Lateral. Pertaining to the side. 
Latticed. (See decussated.) 
Lenticular. Having the shape of a double convex lens, as some bi- 
valves. 
Lithodesma. An accessory shell plate near the umbones, in those 
shells having a “cartilage” or resilium, as in Mactra. 
Lobulate. Composed of lobes. 
Longitudinal, The length of a shell. 
Lunate. Shaped like a half moon (pl. xxxvi, fig. 7),as the aperture 
in some shells. 
Malleated. Appearing as though hammered (pl. xxxii, fig. 1), 
Manducatory. Relating to the apparatus for masticating food. In 
snails, the jaws and radula. 
Marsupium. A part of an animal used asa pouch to contain the young, 
as the gills of Unio. 
Median. Middle, as the middle tooth on the radula. 
Mesocene. The middle cusp on the teeth of the radula. 
Moncecius. Having the sexes united in the same individuai. 
Multifid. Made up of many lobes or projections, as the cusps on some 
radulz. 
Multispiral. Consisting of many whorls, as some fresh-water snails 
(pl. xxxv, fig. 4). 
Nacreous. Pearly or iridescent, as the interior of some Unios. 
Nave. The interior coating of Pisidium and Spherium. 
Nepionic. The second stage of the embryonic shell, as the glochidium 
of Unio. 
Nodulosus. Provided with small knobs or projections, as the surface 
of some Unios (pl. xx, fig. 2). 
Notched. Nicked or indented, as the anterior canal of some gastro- 
pods (pl. xxxv, fig. 5). 
Nucleus. The first part or beginning, as the apex in a univalve and 
the umbo in bivalves. 
Nucleated. Having a nucleus. 
Obconic. In the form of a reversed cone (pl. xxxv, fig. 6). 
Oblique. Slanting, asthe aperture of some shells when rot parallel 
to the longitudinal axis (pl. xxxiv, fig. 7). 
Oblor g. Longer than high, as some Unios (pl. x, fig. 1). 
Obovate. Reversed ovate, as some shells when the diameter is greater 
near the upper than at the lower part. 
Obtuse. Dull or blunt, as the apex of some univalves (pl. xxxv, fig. 9). 
Olfactory. Pertaining to the smell. 
Olivaceous. Colored like an olive. 
Opisthodetic. With the ligament behind the umbones. 
Orbicular. Like an orb or disk, as some Spheria (pl. xxvii, fig. 10). 
Organism. An organized being, or living object made up of organs. 
Ovate. Egg-shaped. 
Ovately conic. Shaped like an egg, but with a somewhat conic apex, 
as some univalves. A, 
