A Conchological Manual by George Brettingham Sowerby (best interesting books to read txt) 📕

   outer lip reflected, denticulated on the inner edge. Suture of the

   whorls covered with enamel.--_Obs._ This genus of shells resembles

   Marginella in form, but has no folds on the columella. Having a scar or

   groove down the back it may be considered intermediate between

   Marginella and Cypræa. Fig. 454, E. Maugeriæ. In the Author's

   Conchological Illustrations, seven species are enumerated and figured.

   ERUCA. Sw. A subgenus of Clausilia. Sw. Malac. p. 334.

   ERVILIA. Turt. A genus described as "oval, equivalve, equilateral,

   closed. Hinge with a single erect tooth closing between two small

   diverging ones in the opposite valve: lateral teeth none. Ligament

   internal. E. nitens. Turt. Mya. nitens, Auct."

   ERYCINA. Lam. _Fam._ Mactracea, Lam. Conchacea, Bl.--_Descr._ Ovate or

   triangular, transverse, equivalve, inequilateral, smooth; hinge with a

   ligamentary pit, two diverging cardinal and two lateral teeth in each

   valve; muscular impressions two in each valve; palleal impressions

   sinuated. East and West Indies and Mediterranean.--_Obs._ This genus is

   distinguished from _Mactra_ and _Lutraria_ by the cardinal teeth being

   placed one on each side of the ligamentiferous pit; whereas in the last

   named genera they are both placed on the anterior side. Fig. 86, E.

   Plebeja.

   ERYTHRÆA. The ancient name for CYPRÆA.

   ESCUTCHEON. The impression on the posterior dorsal margin of some

   bivalve shells. That on the anterior margin is named the lunule. The

   escutcheon is pointed out by the letter _e_ in some of the figures of

   Cythereæ. Fig. 117, _a. b. c._

   ETHERIA. Lam. (_Æther_, air.) Fam. Chamacea, Lam. and Bl.--_Descr._

   Irregular, inequivalve, inequilateral, foliaceous, pearly within,

   covered by an olive green epidermis without; hinge callous, undulated,

   destitute of teeth; ligament partly external, partly internal, passing

   through the hinge on a somewhat raised, callous area in the lower

   valve. Muscular impressions elongated, two in each valve, united by a

   slender palleal impression. Rivers of Africa.--_Obs._ The irregular,

   unequal air-bubbles of the inner surface, whence this genus derives its

   name, are very brilliant in some species, and atone, in some measure,

   for the rugged ugliness of the exterior. In its irregular form,

   foliated structure, and toothless hinge, it resembles OSTREA, from

   which it differs in having two muscular impressions. Fig. 155, E.

   semilunata.

   EULIMA. Risso. _Fam._ Scalariens, Lam.--_Descr._ Elongated, smooth,

   pyramidal; spire long, composed of numerous whorls; apex acute,

   slightly tortuous; aperture oval, rounded anteriorly, acute at the

   posterior union with the body whorl; outer lip slightly thickened;

   columella smooth. Fig. 347, E. labiosa, fig. 348, E. splendidula. A

   complete illustrated monograph of this genus of pretty shining little

   shells, consisting of 15 known species, is given in parts 52 and 53 of

   the Conchological Illustrations by the author.

   EUOMPHALUS. Sow. _Fam._ Scalariens, Lam.--_Descr._ Orbicular,

   planorbular spire, with three or four volutions, imbricated above;

   smooth below; aperture of a round polygonal form; umbilicus large,

   penetrating to the apex of the shell.--_Obs._ This genus of fossils

   very nearly resembles Delphinula. The main difference appears to be

   that the whorls do not increase so rapidly in size in the former as in

   the latter. Fossil, in the Carboniferous Limestone. Fig. 350.

   EXOGYRA. Sow. A genus of fossil bivalves, resembling Chama in shape and

   Ostræa in structure, having but one muscular impression in each valve.

   Fig. 183.

   EXSERTED. Standing out, protruding.

   EXTERNAL. An external shell is one which contains the animal, and is

   not covered by the mantle.

   FASCIATED. (_fascia_, a band.) Banded or striped. Ex. Carocolla

   marginata, fig. 277.

   FASCICULATED. (from fasciculum.) A little bunch of hairs or bristles

   against each end of each valve, characterizes some species of the genus

   Chiton, which are termed fasciculated species.

   FASCIOLARIA. Lam. _Fam._ Canalifera, Lam. Siphonostomata, Bl.--_Descr._

   Elongated, fusiform, ventricose; spire conical, consisting of few

   rounded or angulated whorls; aperture wide, terminating in a long

   straight open canal: columella lip with several oblique folds, the

   lower of which is larger than the rest; operculum horny,

   pyriform.--_Obs._ This genus is known from Fusus by the folds on the

   columella; from Turbinella, by their obliquity and the last being

   larger than the rest. Fig. 386, F. Trapezium. East and West Indies and

   Australia.

   FAUNUS. Montf. MELANOPSIS, Auct.

   FERRUGINEOUS. Of an iron rust colour.

   FERUSSINA. Grateloup. STROPHOSTOMA, Deshayes.

   FIBROUS. A shell is said to be of a fibrous structure when a fracture

   would present a series of perpendicular fibres, as Pinna.

   FICULA. Sw. A generic group of shells, consisting of those species of

   PYRULA, Auct. which have the true pear-shaped character. Fig. 390, P.

   Ficus. Sowerby confines the name Pyrula to these species.

   FIMBRIA. Megerle. CORBIS, Lam.

   FIMBRIATED. Fringed; as Murex fimbriatus, a delicate white species,

   with broad fringed varices.

   FISSURE. (_Fissura_, a slit.) A slit or cut, a narrow perforation, as

   in Emarginula and Fissurella.

   FISSURELLA. Brug. (_Fissura_, a fissure.) _Fam._ Calyptracia, Lam.

   Branchifera, Bl.--_Descr._ Patelliform, oval or oblong, radiated; apex

   anterior, perforated.--_Obs._ The Fissurellæ are known from Patellæ by

   the perforation in the apex. Fig. 245. The catalogue published by the

   author in the Conchological Illustrations, enumerates 68 species.

   FISTULANA. Lam. (_Fistula_, a pipe.) _Fam._ Tubicolæ, Lam. Adesmacea,

   Bl.--_Descr._ A transversely elongated, equivalve, inequilateral

   bivalve, enclosed by a septum within the widest, closed extremity of a

   straight calcareous tube. Fistulana is known from Gastrochæna by the

   straightness of the tubes, and the oblong state of the valves. Fig. 54,

   Fistulana Clava.

   FLEXUOUS. Having windings or bendings. _Ex._ The Tellinæ are known by

   the twist or flexuosity in the posterior ventral margin of the shell.

   FLORILLUS. Montf. A genus of microscopic Foraminifera.

   FLUVIATILE. (Fluviatilis.) Belonging to a river or running stream.

   _Ex._ Limnæa fluviatilis.

   FLUVIATILE CONCHACEA. See CONCHACEA.

   FOLIATED, or FOLIACEOUS. (From _folium_, a leaf.) When the edges of the

   successive layers of which a shell is composed are not compacted but

   placed apart from each other, projecting like tiles, the shell is said

   to be of a foliated structure. The common Oyster, fig. 180, presents a

   familiar example.

   FORAMINIFERA. D'Orb. (_Foramen_, a hole or pit.) An order established

   for minute many chambered internal shells, which have no open chamber

   beyond the last partition. Lamarck, D'Orbigny, and other writers have

   placed them among the Cephalopoda in their systems, but Du Jardin, on

   comparing the fossils with some recent species of the same class,

   arrived at the conclusion, now generally adopted, that they constitute

   a distinct class, much lower in degree of organization than even the

   Radiata. Not recognizing these microscopic bodies as shells, properly

   so called, but considering them sufficiently numerous and interesting

   to form a distinct branch of study, I do not think it desirable to

   describe the genera, or to present any arrangement of them in this

   work.

   FORNICATED. Arched or vaulted, as the exfoliations on the costæ of

   Tridacna Elongata, fig. 157.

   FOSSIL SHELL. A shell is considered to be in a fossil state when, the

   soft parts having ceased to exist, it is deprived of all its animal

   juices, has lost all, or nearly all its natural colour, and is thus

   changed in its chemical composition, when little or nothing is left but

   a mere bone, which is embedded in a sedimentary deposit. In this state,

   it is fragile, prehensile to the tongue, and either destitute of colour

   or tinged with the diluted mineral matters which pervade the stratum in

   which it lies. In some cases, the mineral composition of the shell is

   so completely changed as no longer to present its proper structure,

   consisting of successive oblique layers of shelly matter; but is

   altered into a fibrous structure, composed of rhomboidal particles. An

   example of this will be found in the Belemnites, which if broken, shew

   the perpendicular fibres. In other cases, the matter which has entered

   and filled up the cavities of the shell has become silicified, or

   changed into flint, and the shell itself has been decomposed and fallen

   off, so as to leave nothing but an external or internal cast of its

   form, in flint. This is called a Conchyliomorphite by continental

   writers. Some of the most important of Geological data are obtained by

   a minute comparison of fossil shells, found in various beds, with

   recent ones presenting the nearest resemblance to them. Some species of

   fossil shells are considered as identical with recent species. And many

   Geologists seek to fix the chronology of the different strata by the

   number of species which they inclose bearing a resemblance to the

   recent species. Indeed, all who would study Geology with success, will

   find it indispensably necessary to obtain a thorough knowledge of

   Conchology.

   FRAGELLA. Sw. A sub-genus of Monodonta, corresponding with the genus

   Clanculus, Montf. consisting of M. Pharaonis (fig. 361), and similar

   species. Sw. p. 352.

   FRAGILE. (_Fragilis._) Tender, easily broken.

   FREE SHELL. One that is not attached.

   FREE VALVE. In attached bivalve shells, one only is fixed; the other is

   then _free_, as far as to the action of opening and shutting.

   FRESH-WATER SHELLS, (sometimes described as aquatic) are those which

   either inhabit rivers, running pools and ditches, in which case they

   are _fluviatile_; or wells and ponds of standing water, &c. Fresh-water

   shells are either thin and horny in their texture, as the Limneana of

   Lamarck; or are covered with a compact, smooth, horny epidermis. They

   are generally simple in form, subject to corrosion where the epidermis

   is wounded or broken, and are circumscribed with regard to the classes

   and genera to which they belong. The family of Nayades includes nearly

   all the fresh-water bivalves; and the Melaniana and Limneana are the

   principal among univalves.

   FRONDICULARIA. Defr. A genus of microscopic Foraminifera.

   FRONT. The surface of a shell on which the aperture appears.

   FULCRUM. That part of a shell on which any other part rests or turns.

   The term is applied more particularly to the tumid part in the hinge of

   bivalve shells on which the ligament is fixed.

   FULGUR. Montf. PYRULA perversa, Auct. and such other species as have an

   angulated spire. Fig. 388.

   FUSIFORM. (_Fusus_, a spindle.) Shaped like a spindle, swelling in the

   centre and tapering at the extremities. _Ex._ Fusus, fig. 387.

   FUSUS. Brug. (A spindle.) _Fam._ Canalifera, Lam. Siphonostomata,

   Bl.--_Descr._ Fusiform, turrited, with many rounded whorls; aperture

   generally oval, terminating in a long straight canal; operculum horny,

   pyriform.--_Obs._ The Fusi are subject to considerable variations in

   form. The recent species are numerous and do not appear to be confined

   to any climate. The fossil species are also numerous, chiefly abounding

   in the tertiary formations. The recent species are mostly tropical.

   Fig. 387, F. Colus.

   GALATHÆA. Brug. POTAMOPHILA, Sow. MEGADESMA, Bowd.

   GALEA. Klein. PURPURA, Auct.

   GALEOLARIA. Lam. (From Galea, a helmet or crest.) A genus composed of

   species of SERPULA, Auct. Distinguished as being fixed by the side of

   the shell, and having the anterior extremity erect, the aperture

   terminating in a tongue-shaped projection.--_Obs._ This genus is said

   by Lamarck to resemble Vermilia in other respects, but to differ in

   having the anterior part raised. Fig. 6, G. decumbens. Africa and

   Australia.

   GALEOMMA. Turt. _Fam._ PHOLADARIA, Lam.--_Descr._ Thin, oval,

   equivalve, equilateral, with the ventral margin gaping; hinge with one

   cardinal tooth in each valve; muscular impressions two, approximate;

   palleal impression interrupted, not sinuated; ligament small, partly

   internal, partly external, fixed on a prominent fulcrum.--_Obs._ The

   wide hiatus in the ventral margins of this equilateral shell prevents

   the possibility of confounding it with any other. Four or five recent

   species are known, one of which is found on the coast of Sicily, and

   also in the British Channel. G. Turtoni, fig. 58.

   GALERICULUS. (_Galericulum_, a little cap or bonnet.) VELUTINA, Auct.

   fig. 337.

   GALERUS. Humph. CALYPTRÆA, Lam.

   GAPING. (_Hians._) Bivalve shells are said to gape when the margins do

   not meet all round. _Ex._ Gastrochæna, fig. 52.

   GARI. Schum. PSAMMOBIA, Lam.

   GASTEROPODA. Lam. ([Greek: Gastêr], _gaster_, belly; [Greek: pous,

   podos], _pus_, _podos_, a foot.) The second order of the class

   Mollusca, Lam. containing those molluscous animals whose organs of

   locomotion are ventral. Most of the shells belonging to this order are

   patelliform, placed upon the back of the animals, which rest or crawl

   upon the belly. This order is divided into Pneumonobranchiata, that is,