A Conchological Manual, George Brettingham Sowerby [little readers .TXT] 📗

such

   species of Nautilus as have been compressed, so as to assume an oval

   instead of a round form. The genus Ellipsolites of De Montfort consists

   of species of Ammonites similarly deformed.

 

   NAUTILACEA. Bl. The fifth family of Polythalamacea, Bl. the shells of

   which are described as more or less discoidal, compressed,

   symmetrically convolute; the last whorl much longer than the others;

   which are entirely hidden beneath it and advancing beyond the last but

   one, so as constantly to form a large oval aperture, which is always,

   however, modified by the last whorl. The septa are united in the

   greater number of instances and pierced by one or more (?) siphons.

   This family contains the genera Orbulites, Nautilus, Polystomella and

   Lenticulina.

 

   NAUTILACEA. Lam. The sixth family of Polythalamous Cephalopoda, Lam.

   containing the genera Discorbites, Siderolites, Polystomella,

   Vorticialis, Nummulites, Nautilus. To these may be added Simplegas and

   Endosiphonites. Fig. 472 to 476.

 

   NAUTILUS. Auct. (_A little boat._) _Fam._ Nautilacea, Lam. and

   Bl.--_Descr._ Convolute, discoid, chambered, symmetrical; spire partly

   or entirely concealed by the last whorl; aperture modified by the last

   whorl, wide, sinuated on the dorsal margin; interior surface pearly;

   septa dividing the chambers simple; siphon discontinuous.--_Obs._ The

   shell named Nautilus by Pliny is the Argonauta of modern authors, a

   thin shell, not chambered. The Nautili are known from the Ammonites by

   the septa being simple, not sinuated as in the latter genus, and in

   general the volutions of the spire are not visible. Three or four

   species are known inhabitants of the Pacific Ocean and Australian

   Ocean. The fossil species are found in the tertiary, and also in the

   secondary strata, as low down as the Mountain limestone. N. pompilius,

   Frontispiece.

 

   NAYADES. Lam. A family of the order Conchifera Dimyaria, Lam. described

   as containing fresh-water bivalve shells, with or without teeth on the

   hinge. They are all pearly within, and have a thick, rather smooth

   epidermis without. This family contains a great variety of shells,

   which have been separated into an immense number of genera, but which

B. Sowerby, sen. gives very good reasons for uniting under one

   generic name. The most generally received distinctions are as follows:

 

CASTALIA. Two cardinal, one lateral, ribbed teeth. This genus is

       removed from the family of Trigonacea. Fig. 140.

 

UNIO. Teeth various. Fig. 142, 145, 149, 148, 147, 151, 141.

 

HYRIA. Trigonal, alated. Fig. 143, 150.

 

ANODON. No teeth. Fig. 152.

 

IRIDINA. Hinge crenated. Fig. 150.

 

   NECTOPODA. Bl. The first family Nucleobranchiata, Bl. containing the

   genera Carinaria and Firola; the latter is not a shell.

 

   NEMATOPODA. Bl. The first class of the sub-type Malentozoa, Bl.

   containing all the mollusca with multivalve shells, except Chiton, and

   divided into the families Lepadicea and Balanidea, corresponding with

   Lamarck's sessile and pedunculated Cirripedes, and with the Linnæan

   genus Lepas.

 

   NEMATURA. Benson. _Fam._ Turbinacea, Lam.--_Descr._ Thin, nearly oval,

   somewhat compressed from back to front; spire acute, consisting of few

   rounded whorls; last whorl large, but contracted near the aperture;

   aperture small, oblique, rounded anteriorly; peritreme continuous,

   thin; operculum spiral, horny, with few volutions.--_Obs._ The

   distinguishing character of this genus is the contraction of the last

   whorl near the aperture, in which respect it is nearly resembled by the

   shell called Cyclostoma lucidum. Two recent and one fossil species, all

   very minute, are described by Sowerby in Loudon's Magazine of Natural

   History, New Series. Fig. 305.

 

   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:

 

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

       323.

 

NERITA. Columellar lip septiform, edge with distinct teeth;

       shell thick. Fig. 330.

 

NERITINA. Shell thin; columellar lip septiform, edge

       denticulated; generally a thick, dark coloured epidermis. Fig. 324

       to 326.

 

NATICA. Having an umbilicus behind the columellar lip, with a

       spiral callosity. Fig. 327, 328.

 

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

       331.

 

PILEOLUS. Patelliform; apex central; columellar lip septiform,

       leaving the aperture small. Fig. 332.

 

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.

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.

 

   NYMPHACEA. Lam. A family belonging to the order Conchifera Dimyaria,

   Lam. Ligament external, placed on a prominent fulcrum. This family

   contains the following genera:

 

SANGUINOLARIA. Rostrated, gaping; two cardinal teeth in each

       valve, including _Soletellina_ and _Lobaria_. Fig. 98, 99.

 

PSAMMOBIA. Quadrate; valves closed, including Psammotæa. Fig.

       100.

 

CORBIS. Thick, fimbriated; a cardinal tooth in the centre of a

       pit. Fig. 101.

 

GRATELOUPIA. A series of small teeth filling a triangular area.

       Fig. 102.

 

EGERIA. One single and one double cardinal tooth. Fig. 103.

 

LUCINA. Rounded; anterior muscular impression tongue-shaped.

       Fig. 104.

 

TELLINA. An anterior fold in the ventral margin; lateral teeth.

       Fig. 105, 106.

 

TELLINIDES. No anterior fold; no lateral teeth. Fig. 107.

 

DONAX. Margin denticulated; shell wedge-shaped. Fig. 108.

 

CAPSA. Margin not denticulated, no lateral teeth. Fig. 109.

 

   OBELISCUS. Humph. TROCHUS, Lam.

 

   OBLIQUE. (_obliquus._ lat.) In a slanting direction. The whorls of

   spiral univalves generally take an oblique direction in reference to

   the imaginary axis of the shell. A bivalve is said to be oblique when

   it slants off from the umbones. An example of this is seen in Avicula,

   fig. 163.

 

   OBSOLETE. (_obsoletus_, lat.) Worn out, out of use. This term is used

   to express an indistinctness of character, which sometimes results from

   the action of sea-water upon unprotected parts of the shell, and

   sometimes from the deposits of enamel formed in age, and covering the

   early striæ, ribs, teeth, &c. thereby rendering them less acute.

 

   OBTUSE. (_obtusus_, blunt.) The application of this term is