Part 51

NERINEA. Defr. Fam. Canalifera, Lam.--Descr. Turrited, oblong, sub-canaliculated, consisting of numerous whorls; aperture with a strong fold on the columella, one on the outer lip, and one on the inner lip at the edge of the body whorl.--Obs. This genus is only found in a fossil state usually in the Oolitic beds, it is not resembled by any other; the strong, prominent folds on the three upper angles of the subquadrate aperture present a singular appearance in a section. One species has been named N. Hieroglyphus. We give N. Goodhallii, fig. 374.

NERITA. Auct. Fam. Neritacea, Lam. Hemicyclostomata, Bl.--Descr. Smooth or ribbed, semiglobose; spire short, sometimes flat, consisting of few volutions; aperture large, semilunar; outer lip thick, entire; inner lip thickened, dentated at the edge, spread over the body whorl, forming a flattened disc; operculum shelly, spiral, with an appendage by which it is locked under the sharp edge of the columella.--Obs. These marine shells are known from Neritina by the thickness of the shell and the want of the thick, horny, dark coloured epidermis; from Natica by the flat area produced by the spreading of the thickened columellar lip. N. Peloronta, fig. 330. N. polita, fig. 329.

NERITACEA. Lam. A family of the first order of Trachelipoda, Lam. containing the following genera:

1. NAVICELLA. Apex terminal, not spiral; inner lip septiform. Fig. 323.

2. NERITA. Columellar lip septiform, edge with distinct teeth; shell thick. Fig. 330.

3. NERITINA. Shell thin; columellar lip septiform, edge denticulated; generally a thick, dark coloured epidermis. Fig. 324 to 326.

4. NATICA. Having an umbilicus behind the columellar lip, with a spiral callosity. Fig. 327, 328.

5. NERITOPSIS. Edge of the columellar lip with a deep notch. Fig. 331.

6. PILEOLUS. Patelliform; apex central; columellar lip septiform, leaving the aperture small. Fig. 332.

7. JANTHINA. Columellar lip linear; aperture angulated. Fig. 333.

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.

NONION. Montf. A genus of microscopic Foraminifera.

NONIONINA. D'Orb. A genus of microscopic Foraminifera.

NOTREMA. Rafinesque. A shell described as composed of three integral valves, concerning which De Blainville puts the query, "ne seroit-ce pas plutôt une Balanide mal observée?"

NOVACULINA. Benson. (Novacula, a razor.) Fam. Solenacea, Lam.--Descr. Equivalve, inequilateral, transversely elongated; external ligament communicating with the interior of the shell by an oblique channel; beaks prominent; hinge line nearly straight, with one narrow curved cardinal tooth in one valve, entering between two similar teeth in the other; siphonal scar long; extremities of the shell gaping; epidermis thin, light brown, folding over the edges and connecting the dorsal margins. Hab. Jumna, Gooti, and Ganges. Fig. 63.

NUCLEOBRANCHIATA. Bl. The fifth order of the second section of Paracephalophora Monoica, Bl. the shells of which are described as symmetrical, more or less curved, or longitudinally rolled up and very thin. This order contains, Fam. 1. Nectopoda, containing Carinaria; Fam. 2. Pteropoda, containing Atlanta, Spiratella and Argonauta.

NUCLEUS. (A kernel.) Anything forming a centre around which matter is gathered. The nucleus of shells is the first formed part; the first deposit of shelly matter to which the successive layers are added; the apex of the spiral cone, of which most shells are composed. (See CONE.) The nucleus is formed within the egg in oviparous, and within the old shell in viviparous mollusca. It is frequently more transparent and light than the remainder of the shell, and sometimes falls off; when this occurs the shell is said to be decollated.

NUCULA. Lam. (A small nut.) Fam. Arcacea, Bl. and Lam.--Descr. Equivalve, inequilateral, transverse, covered with an epidermis; hinge linear, with a series of sharp, angulated teeth, arranged in a line on each side of the umbones, and a central ligamentary pit; muscular impressions two, simple; palleal impressions not sinuated.--Obs. The row of teeth on each side of the umbones, and the ligamentary pit in the centre of the hinge prevent the pretty little shells of this genus from being confounded with any other. Thirty-four figures are enumerated in the catalogue by Sowerby, sen. which accompanies the Conchological Illustrations of the author. The new species, to the amount of 24, have been figured in parts 14 to 16, of the above mentioned work. Recent Nuculæ are found from the frozen to the torrid zones, and the fossil species occur in nearly all the beds from the Pliocene to the Carboniferous system.

NUMMULACEA. Bl. The third family of Cellulacea, Bl. described as containing shells or calcareous bodies, which are characterized as discoidal, lenticular; without the slightest traces of whorls to be seen externally. The whorls are numerous, internal, and divided into a great number of cells, which are separated from each other by imperforate septa. This family contains the genera Nummulites, Siderolites, Vorticialis, Helicites, Orbiculina, Placentula.

NUMMULTTES. Lam. (Nummus, money.) Fam. Nautilacea, Lam.--Descr. Orbicular, convolute, shewing no trace of spire externally; interior divided into cells spirally arranged.--Obs. The singular fossils composing this genus receive their name from their external resemblance to a battered coin. Fig. 472. N. lenticulina.

NUX. Humph. CYCLAS, Lam.