NERITINA. Lam. _Fam._ Neritacea, Lam.--_Descr._ Thin, semiglobose, obliquely oval, smooth, flattish in front; spire short, sometimes depressed, consisting of few rapidly increasing whorls; aperture semicircular; outer lip thin, sharp; columellar lip broad, flat, its inner edge straight, denticulated; operculum testaceous, semicircular, sub-spiral, with an articulating process on the inner edge.--_Obs._ This genus of fresh-water shells differs from Nerita in the minuteness of the denticulation of the columella, as well as in the characters mentioned in our observations upon the latter genus. N. spinosa, (Clithon, Montf.) fig. 325. N. virginea, fig. 324. N. perversa, Lam. (Velates, Montf.) fig. 326. All the species known up to the present time, with the exception of three, are represented in the author's Conchological Illustrations, parts 86, 87, 90, 91, 94 to 100. The catalogue accompanying these representations enumerates 59 species. NERITOPSIS. Gray. _Fam._ Neritacea, Lam.--_Descr._ Sub-globose, thick, cancellated; spire short, composed of few rapidly increasing whorls; aperture transverse, sub-orbicular; outer lip thickened within; columellar lip thick, rather flat, with a large rounded notch in the centre of its inner edge.--_Obs._ This genus most nearly resembles Nerita, from which it differs in the peculiar notch of the columella. N. granosa, fig. 331. NICANIA. Leach. ASTARTE, Sowerby. The same as CRASSINA of Lamarck. NITIDELLA. Sw. A genus of "Columbellinæ," Sw. thus described: "Bucciniform, small, ovate, smooth, glassy; aperture effuse; outer lip slightly thickened, faintly inflexed, and generally striated internally; inner lip somewhat flattened above; base of the pillar with one or two slight internal folds, or a single angular projection. Columbella nitida, _Lam._ (fig. 17, _c._ p. 151.)" Sw. p. 313. NOBIA. Leach. _Order_, Sessile Cirripedes, Lam. This genus resembles Pyrgoma, Auct. consisting of a conical paries, supported upon a funnel-shaped cavity in the madrepore, but differs in its operculum, which consists of two valves, whereas that of Pyrgoma has four. N. grandis, fig. 29. NODOSARIA. Lam. and ORTHOCERA have been united by Sowerby under the name of the first. _Fam._ Orthocerata, Lam. and Bl.--_Descr._ Straight, chambered, elongated; chambers more or less ventricose; septa perforated by a central siphon.--_Obs._ This genus consists only of fossils found in sub-appenine tertiary beds. It is placed by De Blainville in one of his divisions of the genus Orthoceras, which is characterized as "species not striated, and with chambers very much inflated." N. æqualis, fig. 465. NODOSE. Having tubercles or knobs. NOGROBS. Montf. A fossil appearing from the figure and description to resemble Belemnites.