Front matter (continued 3)

CLEODORA. Per. et Les. Fam. Pteropoda, Lam. Thecosomata, Bl.—Descr. Thin, transparent, pyramidal, with flat alate sides, and oval aperture. Fig. 221, C. cuspidata.

CLISIPHONITES. Montf. Microscopic. Lenticulina, Bl.

CLITHON. Montf. Neritina Corona, spinosa, &c. Auct. fig. 325.

CLITIA. Leach. Fam. Balanidea, Bl. Order, Sessile Cirripedes, Lam.—Descr. Sub-conical, compressed, consisting of four unequal valves, two larger and two smaller, joined together side by side, by the interlocking of their dentated edges, a process somewhat like that which joiners call dove-tailing. Operculum, consisting of two unequal pointed valves.—Obs. Clitia is known from Creusia, by the articulations of the valves, and by the operculum, which in Creusia consists of four valves. Fig. 20. C. Verruca, (Lepas Verruca, Gmelin.) Britain and Peru.

CLOSE. The margins of a bivalve shell are described as being close, when there is no hiatus between them in any part, otherwise they are described as gaping.

CLOTHO. Faujas. Fam. Conchacea, Bl. More properly belonging to the Pyloridea, Bl.; and the Lithophagidæ, Lam.—Descr. "Oval, nearly regular, longitudinally striated, equivalve, sub-equilateral; hinge consisting of a bifid tooth, curved like a crochet, larger in one valve than in the other." This description is translated from Blainville, who states that he has never seen the shell. Annales du Museum D'Histoire Naturelle, tom. 9, pl. 17, fig. 4-6.

CLYPEIFORM. (Clypeus, a shield.) Open, flat, shaped like a shield or buckler, as Umbrella, fig. 233, and Parmophorus, fig. 242.

CLYPIDELLA. Sw. A sub-genus of Fissurella, described as having one extremity of the shell slightly raised. C. pustula. Sow. Gen. fig. 3.

COAT OF MAIL. A common name given to shells of the genus Chiton, on account of their resemblance to jointed armour.

COBRESIA. Hübner. Vitrina, Auct.

COCHLIATE. (Cochleare, a spoon). Applied to any shell or part which is hollow and oval, as Patellæ, &c. The cavity containing the cartilage in Mya, fig. 71, is Cochleate.

COCHLICELLA. One of the sub-genera into which De Ferrusac has divided the genus Helix, consisting of Bulinus decollatus, fig. 279, and similar species. See Helix.

COCHLICOPA. Fer. A sub-genus of Helix, partly corresponding with Polyphemus of De Montfort, and consisting of species of Achatina, which have the outer lip undulated.

COCHLITOMA. Fer. A sub-genus of Helix, corresponding with the genus Achatina, Auct. not including those with undulated outer lips.

COCHLODINA. Fer. A sub-genus of Helix, including the genus Clausilia, Auct.

COCHLODONTA. Fer. A sub-genus of Helix, containing Pupa Uva, Auct. &c.

COCHLOGENA. Fer. A sub-genus of Helix, containing pupiform shells, such as Azeca tridens, fig. 290.

COCHLOHYDRA. Fer. A sub-genus of Helix, composed of the genus Succinea, Auct.

COCHLOSTYLA. Fer. A sub-genus of Helix, composed of the genus Bulinus, Auct.

COLIMACEA. Lam. This Family, of the order Trachelipoda, Lam. includes all land shells, which might with propriety be divided into three sections, the first of which contain the following well-known genera:—

1. Succinea. Oval, transparent, oblique; animal amphibious. Fig. 265, 266.

2. Helix. The type of which is the common snail shell. The separation of Carocolla, on account of the angulated whorls, or that of Geotrochus, on account of the turbinated shape, cannot be well maintained. Fig. 264, 267, 268, 273 to 276, 278 to 281, 294.

3. Anostoma. The aperture turned up towards the spire. Fig. 271, 272.

4. Streptaxis. Whorls excentric. Fig. 269, 270.

5. Bulinus. Oval; aperture entire, including Bulimulus, Balea, Cionella, Azeca. Fig. 282 to 285, 289, 290, 296.

6. Achatina. A notch terminating the columella. Fig. 286 to 288.

7. Pupa. Cylindrical; including Vertigo, Alæa, &c. Fig. 291 to 293.

8. Clausilia. Cylindrical, with a clausium. Fig. 295.

Obs. The above are united in the system of De Ferrusac under the generic name Helix, and divided into sub-genera as explained under that word.

The next section, included in the family Auriculacea, Bl., contains the genera Auricula, Chilina, Carychium, Marinula, Scarabæus, and Partula. Fig. 297 to 302.

The third section contains the following genera of land shells with opercula.

1. Cyclostoma. Aperture round; operculum spiral. Fig. 303, 304.

2. Nematura. Last whorl contracted; operculum spiral. Fig. 305.

3. Helicina. Aperture semi-lunar or angulated; operculum concentric. Fig. 306, 307.

4. Pupina. Shell polished; operculum concentric; aperture round. Fig. 524.

5. Strophostoma. Aperture turned up towards the spire, like Anostoma, but said to have an operculum. Only known fossil. Fig. 97.

COLUMBELLA. Auct. (Columba, a dove.) Fam. Columellata, Lam.—Descr. Thick, oval, or angular; with short spire, and long narrow aperture, contracted in the centre, and terminating in a short canal; outer lip thickened and dentated; inner lip irregularly crenated. Epidermis thin, brown. Operculum very small, horny.—Obs. Those species of Mitra, which resemble Columbella in shape, may easily be distinguished by the plaits on the columella. The Columbellæ are marine, and few fossil species are known. Fig. 430, C. Mercatoria. Swainson has divided this genus into the following: Columbella, consisting of C. Mercatoria, &c.; Pusiostoma, consisting of the Strombiform species; Crassispira, which is most probably a Cerithium; Nitidella, consisting of the smooth species; Conidea, consisting of the more conical species; another set of the more conical species has been removed from this family, and placed in that of the "Coninæ," but as they are separated by no essential character, we suppose this has merely been done for the purpose of completing the "circle" of the last mentioned family, which otherwise would not have reached the required number of five. Mediterranean, East and West Indies, South America, Coast of California, Gallapagos, &c.

COLUMELLA. A solid column formed by the inner sides of the volutions of a spiral univalve. It is sometimes described as the inner lip of the aperture, of which it forms a part; but the term would be more properly confined to that portion of the inner lip which is seen below the body whorl, over which the remainder of the lip is frequently spread. All the inner edge of the aperture, including that part of it which covers the body whorl, is called the columellar lip. In fig. 431, the anterior termination of the columella is indicated by the letter c. The axis, is an imaginary line drawn strictly through the centre of the whorls, whether their inner edges form a solid column or not.

COLUMELLAR LIP. The inner lip. See Columella.

COLUMELLATA. Lam. A family of the order Trachelipoda, Lam. containing the following genera:—

1. Mitra. Elongated; aperture narrow; strong folds on the columella; including Mitrella, Mitreola, Tiara, and Conohelix. Fig. 431, 432.

2. Marginella. Outer lip reflected; including Volutella, Persicula, Gibberula, and Glabella. Fig. 437.

3. Columbella. Outer and inner lips denticulated or granulated. Fig. 430.

4. Voluta. Outer lip thickened; folds on the columella; aperture generally wide; apex papillary; including Scaphella, Harpula, Volutilithes, Cymbiola. Fig. 433, 436.

5. Melo. Shell comparatively light; spire short, sometimes hidden; apex round, spiral; folds on the columella laminar. Fig. 435.

6. Cymba. Upper edge of the aperture separated from the body whorl by a flat disc; apex mammillated, irregular; folds on the columella. Fig. 434.

7. Volvaria. Cylindrical; aperture long, narrow; folds on the columella; spire hidden. Fig. 439.

COLUS. Humphrey. Fusus, Lam.

COMPLANARIA. Sw. A subgenus of Alasmodon (Unio), thus described, "shell winged; the valves connate; the bosses very small and depressed; cardinal teeth two or three; lateral teeth represented by irregular grooves. C. gigas (Unio), Sow. Man. fig. 141. Alasmodon complanatus, Say. C. rugosa, Sw."

COMPRESSED. Pressed together, or flattened. The application is the same as in common use. A Patella may be described as a vertically compressed cone. A Ranella, on account of the two rows of varices skirting the whorls, appears, as it were, laterally compressed. A bivalve shell is said to be compressed when it is flat, that is, when but a small cavity is left in the deepest part when the valves are closed. Perhaps the Placuna placenta, fig. 184, is the most remarkable instance of this.

CONCAMERATIONS. (Con, with, camera, a chamber.) A series of Chambers joining each other, as in Nautilus, Spirula, &c.

CONCENTRIC. A term applied to the direction taken by the lines of growth in spiral and other shells, (longitudinal of some authors.) Every fresh layer of shelly matter forms a new circle round an imaginary line, drawn through the centre of the spiral cone, down from the nucleus. When the edges of the successive layers are marked by any external characters, the shell is said to be concentrically striated, banded, grooved, costated, &c. A fine illustration of the latter is to be seen in the Scalaria or Wentletrap, fig. 351, Lines, bands, ribs, &c. in the opposite direction, (transverse of some authors,) are "radiating" in bivalves, as the ribs of Cardium, fig. 123, and "spiral" in univalves, that is, following the direction of the whorls, as the bands of colour in Pyramidella, fig. 342.

CONCHACEA. Bl. The eighth family of the order Lamellibranchiata, Bl. The shells are described as follows: nearly always regular, valves closed all round; apices curved towards the anterior; dorsal hinge complete, with teeth and ligament; the latter external or internal, short and thick; two distinct muscular impressions, united at the lower part by a parallel impression, which is frequently sinuated at the posterior. The genera described in this family are divided into three sections. First, those which are regular, and have distant lateral teeth, Cardium, Donax, Tellina, Lucina, Cyclas, Cyprina, Mactra, and Erycina. Second, those which are regular, and have no distant lateral teeth, Crassatella and Venus. Third, those which are irregular, Venerupis, Coralliophaga, Clotho, Corbula, Sphænia, and Ungulina.

CONCHACEA. Lam. A family of Lamarck's order Conchifera Dimyaria. Regular, unattached in general, closed at the sides. They are always more or less inequilateral. The Marine Conchacea are those which inhabit the sea. The fluviatile Conchacea are those which are found in rivers, ponds, &c. Each of these contain various genera, which may be arranged as follows:—

Fluviatile.

1. Cyrenella. Three cardinal teeth; ligament long; shell thin. Fig. 114.

2. Cyclas. Thin, oval; cardinal and lateral teeth; anterior side shortest, including Pera.

3. Pisidium. The same, with the posterior side shortest. Fig. 112.

4. Cyrena. Thick; cardinal and lateral teeth. Fig. 113.

5. Potamophila. Two thick cardinal teeth. Fig 115.

Marine.

1. Cyprina. Two cardinal teeth, and one remote lateral tooth. Fig. 116.

2. Venus. Three cardinal, no lateral teeth; including Artemis. Fig. 118, 119, 119a.

3. Cytherea. Several cardinal teeth; one very short lateral tooth. Fig. 117, 117a, 117b, 117c, 117d.

4. Pullastra. Cardinal teeth notched, otherwise like Venus. Fig. 120.

5. Astarte. Three cardinal teeth; ligament short. Fig. 110.

6. Venericardia belongs to the Cardiacea.

CONCHIFERA. Lam. The 11th class of Invertebrata, consisting of all those animals which have bivalve shells. Lamarck divides the class into Dimyaria, which have two adductor muscles; and Monomyaria, which have but one.

CONCHOLEPAS. Montf. (Concha, a shell; lepas, a stone or rock.) Fam. Purpurifera, Lam. Entomostomata, Bl.—Descr. Oval, imbricated, thick; with a very short spire and large oval patelliform aperture, terminating anteriorly in a slight emargination; outer lip crenated, with two produced points or teeth towards the anterior, inner lip smooth, nearly flat, reflected over the last whorl, so as nearly or entirely to cover it; operculum horny. Marine, only one species known, from Peru.—Obs. This shell is placed near Patella by Lamarck, on account of its large open aperture; but having a horny operculum, and resembling Purpurea in other respects. Fig. 418. Concholepas Peruviana.

CONCHOTRYA. Gray. (Concha, a shell; Τρυο, (tryo) to bore.) Order, Pedunculated Cirripedes, Lam.—Descr. Five pieces, two pairs ventral, one single; shaped like Pentelasmis. Found in holes.

CONCHYLIOMORPHITE. A term used by De Blainville to designate the cast or model of a fossil shell, formed by a siliceous substance which has entered or surrounded it when in a liquid state, and subsequently become hardened into flint. The shell has afterwards decomposed or fallen off by accident, leaving its external or internal characters to be conjectured from the monumental impressions that remain.

CONCHYTA. Hupsch Mus. Calceola, Lam.

CONE. A common name for shells of the genus Conus.

CONE. This mathematical term is used by conchologists in its utmost latitude of signification to express a body, which in its formation, commences in a small point, called the apex, and increases in width towards the conclusion or base. It is applied to all shells, whether the increase in width be gradual or sudden; or whether in its growth, it takes a straight, oblique, curved, or spirally-twisted course. In this sense, a bivalve would be described as a pair of rapidly enlarging, oblique cones, and the aperture of every spiral shell would be its base. But this phraseology being in disuse, it is only mentioned here that it may be understood when occasionally met with.

CONELLA. Sw. A genus composed of species of the genus Columbella, Lam. which have a conical form, and which, on that account, are considered by Swainson as belonging to his family of Coninæ. Swains. Lardner. Cyclop. Malac. described at p. 312. C. picata, Sw. fig. 17, a. p. 151.

CONFLUENT. A term applied to two parts of a shell when they gradually flow into each other, as, for instance, the inner and outer lips of Univalves when they pass into each other at the anterior extremity, without the intervention of a notch or angle.

CONIA. Leach. Fam. Balanidea. Order, Sessile Cirripedes, Lam.—Descr. Four rather irregular valves, of porous structure, placed side by side, so as to form a circular cone, supported at the base on a shelly plate, and closed at the aperture by an operculum consisting of four valves in pairs. Distinguished from Creusia by its porous structure and by its flat support; that of Creusia being cup-shaped. Fig. 21, Conia porosa.

CONICAL. A term applied in the ordinary sense, and not as explained above, under the word Cone.

CONIDEA. Sw. A genus separated from Columbella, Lam. thus described, "Mitra shaped, fusiform; spire equal or longer than the aperture; the whorls tumid; outer lip slightly gibbous above, contracted below; margin not inflected; striated within; inner lip terminating in an elevated ridge, but with the teeth obsolete. C. semipunctata, (Columbella, Lam.) Mart. 44. fig. 465, 466." Africa.

CONILITES. Fam. Orthocerata, Lam. & Bl.—Descr. "Conical, straight or slightly curved; having a thin external covering, independent of the nut or alveole, which it contains. Alveole transversely chambered, sub-separable." (Translated from Lam.)—Obs. The difference between Belemnites and Conilites is that the external sheath of the latter is thin, and not filled up with solid matter, from the point of the alveole to the apex, as in the former. De Blainville places in this genus the genera Thalamulus, Achelois and Antimomus, Montf. two of which are figured, Knor. Sup. Fab. iv. fig. 1. 1. 8. 9. Conilites Pyramidatus, fig. 470.

CONILITHES. Sw. A sub-genus of Coronaxis, Sw. (Coni, with coronated whorls) thus described, "Conic; spire considerably elevated; the aperture linear, C. antediluvianus, Sow. Gen. f. 1."

CONOHELIX. Sw. (Conus and Helix.) The generic name given to those species of Mitra which are conical in form. Fig. 432, C. marmorata.

CONOPLÆA. Say. Order, Sessile Cirripedes, Lam. A genus composed of Balani, attached to the stems of Gorgonia, having their bases elongated. Ex. fig. 27, Balanus Galeatus.

CONORBIS. Sw. A genus composed of species of Conus, such as C. dormitor, (Sowerby, gen. fig. 8) which have elevated spires and the upper part of the outer lip deeply sinuated. Mr. Swainson considers these fossil species as analogous to the Pleurotomæ. Sw. Lard. Cyclop. Malac. p. 312.

CONOVULUM. A genus proposed by Lamarck, to include the small, conical species of Auricula, which have the outer lip simple. This genus was afterwards abandoned by the author. Ex. fig. 298, Auricula coniformis.

CONTIGUOUS. (Contingo, to touch.) A term applied to the whorls of spiral shells when they rest upon, or touch each other. This is the case in a great majority of instances. When, on the contrary, there is a space between the whorls, they are said to be non-contiguous, detached, or free. Examples of non-contiguous whorls are to be seen in Scalaria, fig. 351 (in this case, the distance between the whorls is small), and in Crioceratites, fig. 482. A "Columella contiguous to the axis," is when in the centre of the shell and takes the place of the imaginary line which forms its axis.

CONTINUOUS. Carried on without interruption, as the siphon in Spirula, the varices in Ranella, fig. 394, which, occurring in a corresponding part of each whorl, form a continuous ridge.

CONULARIA. Miller. A genus of Orthocerata, described as conical, straight, or nearly so, divided into chambers by imperforate septa; aperture half closed; apex solid, obtuse; external surface finely striated. Resembling Orthoceras, but wanting the siphon. Fig. 449.

CONUS. Auct. (Κωνος, a cone.) Fam. Enroulées, Lam. Angyostomata, Bl.—Descr. Conical, convolute, with a short spire, consisting of numerous whorls; and narrow lengthened aperture, terminating in a slight emargination at each extremity; outer lip thin; epidermis thin; operculum small, pointed, horny.—Obs. This well-known genus of shells is easily distinguished from any other, by its conical form, its smooth columella, its narrow aperture, and thin outer lip. The form of the spire varies from flat and even partially concave, to a regular pyramidal cone; and the upper edges of the whorls are rounded in some species, angulated in others, and in some are waved or coronated. The variety of marking and the numerous delicate tints of these shells have caused them to be highly appreciated by amateur collectors; and many species, as the C. Ammiralis, or admiral; the C. Gloria Maris, or Glory of the Sea; the C. Cedonulli ("I yield to none"), and others, have always produced good prices in the markets. We give figures of the principal forms, as expressed in the genera proposed by De Montfort, of Rhombus, Hermes, Rollus and Cylinder, in figures 459 to 462. Many new species were brought to this country by Mr. Cuming, and are represented in parts 24, 25, 28, 29; 32, 33, 36, 37; 54, 55, 56, 57; 147, 148; 151 to 158 of the Conchological Illustrations, by G. B. Sowerby, jun. See Coronaxis, Swainson. The cones are mostly tropical, some are found as far north as the Mediterranean, and south as the Cape of Good Hope. The most beautiful species are from the East and West Indies.

CONVOLUTÆ. (Enroulées, Lam.) A family of the 2nd section of the order Trachelipoda, Lam. the genera of which may be distinguished as follows:—

1. Cypræa. Lips thickened, inflected, with teeth; spire hidden, including Cypræovulum, Luponia, Trivia. Fig. 444 to 450.

2. Ovulum. Lips thickened, inflected, with slight crenulations; spire hidden. Fig. 440 to 443.

3. Erato. Lips thickened, inflected; spire visible; a groove down the back. Fig. 454.

4. Terebellum. Cylindrical, open at the anterior extremity; columella smooth; suture of the spire canaliculated. Fig. 451, 452.

5. Oliva. Columella plaited, swelled into a varix at the anterior. Fig. 457, 458.

6. Ancillaria. The same, but the suture of the spire covered with enamel. Fig. 455, 456.

7. Conus. Turbinated, numerous whorls; spire flat or short, conical; columella smooth. Fig 459 to 462.

CONVOLUTE. (Con, together; volvo, to revolve). This term can be strictly applied only to symmetrical shells, signifying that the volutions are parallel to each other in a horizontal direction, as in the Ammonites, &c.; but the term is also commonly used in describing such shells as Conus, in which, the direction of the whorls being scarcely oblique, the last whorl almost entirely covers those which precede it. This is the case with Lamarck's family of Enroulées. Fig. 440 to 462.

CORALLIOPHAGA. Bl. Cypricardia Coralliophaga, Lam.—Descr. Oval, elongated, finely striated from the apex to the base, cylindrical, equivalve, very inequilateral; umbones slightly raised and quite anterior; hinge nearly the same in both valves; two small cardinal teeth, one of which is bifid, placed before a kind of lammellated tooth, beneath a very slender external ligament; two small, distant, muscular impressions, united by a striated palleal impression, which is strongly striated posteriorly.—Obs. This shell, which is found in the empty holes of dead Lithodomi, in some instances conforming its shape to its situation, differs from Cypricardia of Lamarck, principally in its cylindrical form. C. Carditoidea, fig. 92. Mediterranean and East Indies.

CORBICULA. Megerle. Cyrena, Lam.

CORBIS. Cuv. (A basket.) Fam. Nymphacea, Lam.—Descr. Transverse, oval, thick, ventricose, equivalve, sub-equilateral, free, cancellated, with denticulated internal margins; hinge with two cardinal and two lateral teeth in each valve; of the latter, one near and one remote from the umbones; muscular impressions lunulate, two in each valve, united by an entire palleal impression, without a sinus.—Obs. This genus, of which only two or three recent species are known, resembles many species of Venus and Cytherea in general form; but differs in having lateral teeth, and in the palleal impressions which in all the Veneres, &c. is sinuated. From Lucina it may be known, not only by its oval form, but also by the muscular impressions, which, in Lucina are produced into an elongated point; it will also be distinguished from Tellina, by the want of a posterior fold in the valve, for which that genus is remarkable. C. Fimbriata, fig. 101, is an inhabitant of the Indian Ocean. Several fossil species are found in the recent formations, above the chalk, at Grignon and Hauteville.

CORBULA. Brug. (A little basket.) Fam. Corbulacea, Lam. Conchacea, Bl.—Descr. Inequivalve, sub-equilateral, transverse, gibbose, not gaping; cardinal tooth in each valve, conical, curved, prominent, inserting its extremity into a pit in the opposite hinge; cartilage attached to the tooth of the smaller valve, and the pit in the larger; muscular impressions, two in each valve, distant, rather irregular; palleal impression posteriorly angulated.—Obs. The shells composing this genus were placed in Mya by Linnæus, but differ from the true Myæ in having a sinus in the palleal impression, and a prominent ligamentiferous tooth in each valve, whereas the Myæ have but one. The Corbulæ are marine, some species inhabiting the British coasts. Fossil species occur abundantly in green sand, London clay, crag, and corresponding formations. Fig. 89. C. Nucleus.

CORBULACEA. (Corbulées, Lam.) A family of the order Conchifera Dimyaria, Lam., containing the genera—

1. Corbula, with a prominent curved tooth. The Fresh-water species has been separated under the name Potamomya. Fig. 89.

2. Pandora. Thin, pearly, no teeth. Fig. 90.

CORDIFORM. (Cor, a heart.) Heart-shaped, a term applied generally to any shell which may be fancied to resemble a heart in shape, as Isocardia, fig. 126, and Cardium Dionæum, fig. 122.

CORIACEOUS. (Corium, leather.) Of the substance of leather. Ex., the integument into which the valves of Chitones are inserted.

CORIOCELLA. Bl. The animal designated by this name is described by De Blainville as being without any traces of shell, either internal or external. This must have arisen from the imperfection of the specimen described, probably deprived by accident of its shell. The testaceous appendage of the Coriocella is now well known to naturalists. It is a milky white, transparent shell, shaped like Sigaretus.

CORNEA, and Pisum, Megerle. Cyclas, Lam.

CORNEO-CALCAREOUS. A term used to express the mixture of horny and shelly matter which enters into the composition of some shells, Aplysia, for instance. It is also applied to those Opercula, which are horny on one side, and testaceous on the other, as that of Turbo.

CORNEUS. Horny. A species of Patella has had the specific name corneus given to it, because its texture more nearly resembles that of a horn than that of a shell. The epidermis of fresh-water shells is of a similar composition.

CORNUCOPIA. Humph. Lepas, Linn.

CORONALES. See Coronular Multivalves.

CORONATED. (Corona, a crown.) Applied to shells when ornamented with a series of points, tubercles, &c., round the upper edges of the volutions. Ex. Conus Nocturnus, fig. 459.

CORONAXIS. One of the two genera into which Swainson divides the genus Conus, consisting of those species which have a row of tubercles on the upper edge of the whorls, an arrangement by which he would in many instances, not only separate between two individuals of the same species, but also between two parts of the same shell; for instances occur in which the earlier whorls are coronated, while the body whorl and the penultimate are perfectly plain.

CORONULA. (Corona, a crown, dim.) Order, Sessile Cirripedes, Lam. Fam. Balanidea, Bl.—Descr. Six radiated valves, joined side by side in a circle, forming a depressed cone; internal structure of the valves, porous or chambered; thickened at the base; operculum consisting of four valves in pairs; imbedded horizontally in a cartilaginous substance.—Obs. The shells composing this genus are found partly imbedded in the skin of whales, and the shells of tortoises, and are therefore destitute of the shelly foundation on which the Balani and other Coronular Multivalves are supported. C. Testudinaria, (Chelonobia, Leach,) fig. 15. C. Balænarum, (Cetopirus, Ranz.) fig. 16. C. Diadema, (Diadema, Ranz.) fig. 17.

CORONULAR MULTIVALVES are those which have their parietal valves joined together side by side in a circle, surrounding the body of the animal, so as to form a sort of coronet. This is the characteristic of the Sessile Cirripedes of Lamarck's system, the Balanidea of De Blainville.

CORRODED. (Corrodo, eat away, consume.) The umbones, apices, and other thick parts of shells, are frequently worn away or consumed by the action of the element in which they exist. As the thickest parts of some shells are the most subject to this operation, it appears to the author to arise from the outer surface of the shell, being less under the influence of the animal juices than the other parts; and therefore, more exposed to the influence of the surrounding element. This, however, is not the case with respect to the Nayades and other fresh-water shells; with these, corrosion does not take place until after the thick epidermis which covers them, becomes wounded by some means or other, and then the animal thickens its shell within as fast as it is corroded without.

CORTALUS. Montf. (Conch. Syst. 1. 115.) A genus of microscopic Foraminifera, placed by De Blainville in a division of the genus Rotalites.

COSTATED. Ribbed, as Cardium Angulatum, fig. 123.

COSTELLARIA. A sub-genus of the genus Tiara, Sw. (Mitra.) C. rigida. Swainson, Zool. Ill. 1st series, pl. 29.

COWRY. A common name for shells of the genus Cypræa.

CRANIA. (Cranium, a skull.) Fam. Rudistes, Lam. Order, Pallio-branchiata, Bl.—Descr. Inequivalve, equilateral, irregular, sub-quadrate; upper valve patelliform, conical, with the umbo near the centre; lower valve attached by its outer surface; muscular impressions, 4 in each valve; two large, posterior, distant; two small, near to each other, central. No hinge teeth; no ligament.—Obs. This genus properly belongs to the Brachiopoda, Lam. It differs from Orbicula in the mode of attachment, which in the latter, is by a byssus passing through the lower valve, and not by the valve itself. Hipponyx has only two muscular impressions in each valve. The name of this genus is derived from the inner surface of the attached valve, which presents a remarkable resemblance to the facial portion of a human skull. This appearance is caused by the situation and elevated edges of the muscular impressions. Fig. 197. Coasts of Britain and Mediterranean.

CRASSATED. (Crassus, thick.) Used to express a thickness in the substance of a shell. Ex. Glycimeris, fig. 67.

CRASSATELLA. Lam. (Crassus, thick.) Fam. Mactracea, Lam. Conchacea, Bl.—Descr. Equivalve, inequilateral, close, thick, rounded anteriorly, rostrated posteriorly, with denticulated margins, smooth, or ribbed transversely; hinge with a triangular pit containing the cartilage, two anterior cardinal teeth, and a posterior depression in one valve; one anterior tooth and a slight anterior marginal elevation, and a posterior elevation in the other valve. Muscular impressions distant, strongly marked. Palleal impression not sinuated.—Obs. The few recent species known are marine, several being brought from the coasts of New Holland. Fossil species are found in Calcaire-grossier and London clay. The Crassatella are known from the Veneres, &c., by the ligamentary pit in the hinge, and from Lutraria and Mactra by the thickness and closeness of the shell. Fig. 84, C. rostrata.

CRASSINA. Lam. Astarte, Sow.

CRASSIPEDES. Lam. (Crassus, thick; pes, foot.) The first section of the order Conchifera Dimyaria, Lam. In this section the foot of the animal is thick, and the shell gapes considerably. It is divided into the families Tubicolæ, Pholadidæ, Solenidæ, and Myaria. Fig. 44 to 76.

CRASSISPIRA. Sw. A genus separated from Columbella, Auct. for which Mr. Swainson quotes "Pleurotoma Bottæ, Auct." Crassispira fasciata, Sw. Lardn. Cyclop. Malac. p. 313.

CRENATED. (Crena, a notch.) Applied to small notches, not sufficiently raised or defined, to be compared to teeth. Ex. The hinge of Iridina, fig. 150.

CRENATULA. Lam. Fam. Malleacea, Lam. Margaritacea, Bl.—Descr. Compressed, foliated, irregular, sub-equivalve, inequilateral, oblique; umbones terminal; hinge linear, nearly straight, with a series of excavations, containing the cartilage, while the intervening ridges are covered with the ligament, properly so called. Muscular impression oblong, indistinct.—Obs. This genus is known from Perna by the hinge, which in the latter is composed of a series of regular, straight, ligamentary grooves placed across it. In Crenatula also there is no passage for the byssus, as in Perna. C. Mytiloides, fig. 168. Coasts of the Red Sea.

CRENULATED. Finely crenated or notched.

CREPIDULA. Lam. (Crepidula, a little slipper.) Fam. Calyptracea, Lam. and Bl.—Descr. Oval, irregular, patelliform; apex lateral, incurved, or sub-spiral; external surface convex, smooth, ribbed, waved, or covered with spines; interior concave, smooth, with a flattish septum reaching nearly half across the cavity; epidermis light brown.—Obs. The difference between this genus and Calyptræa is that in the latter, the septum is more free from the sides of the shell, so that, instead of forming a regular plate, covering half the aperture, it assumes a variety of shapes, and in some is cup-shaped, in others forked, and in some forms a little angular shelf. Indeed, the variations are so numerous that I think it would be better to throw the two genera into one, and then divide them into smaller groups. Some species of Calyptræa are farther removed from each other with respect to the characters of the septum and general form of the shell, than they are from the Crepidulæ. Fig. 239. Mediterranean, North and South America, East and West Indies, New South Wales, &c.

CREPIDULINA. Bl. Cristellaria, Lam. Microscopic.

CRESEIS. Ranz. Order, Pteropoda, Lam.—Descr. Thin, fragile, transparent, pyramidal, pointed; with a dorsal ridge produced into a point at the edge of the aperture.—Obs. The species found in the Mediterranean is named C. Spinifera (fig. 222), from its resemblance to a thorn.

CREUSIA. Leach. (Creux, se. Fr. a cavity.) Fam. Balanidea, Bl. Order, Sessile Cirripedes, Lam.—Descr. A depressed cone, consisting of four valves, supported upon, and jointed to, a cup-shaped cavity formed in the Madrepores, in which it resides. Aperture quadrilateral, closed by an operculum of four valves.—Obs. This genus is distinguished from Pyrgoma, which is supported on the edge of a similar cup-shaped cavity, by the paries being composed of four valves, whereas in Pyrgoma, it consists of a single piece. Fig. 28, C. Gregaria. East Indies.

CRICOSTOMATA. Bl. The second family of Asiphonibranchiata, Bl. It is thus described: "shell equally (with the animal) variable in general form, but of which the aperture, always nearly round, is completely closed by the shelly or horny operculum; whorls few, and apex sublateral." This family agrees in some measure with the family Turbinacea of Lamarck, and with the genus Turbo in the system of Linnæus. It contains the genera Pleurotomaria, Delphinula, Turritella, Proto, Scalaria, Vermetus, Siliquaria, Magilus, Valvata, Cyclostoma, and Paludina.

CRIOCERATITES. A genus composed of species of Ammonites, with disconnected whorls. C. Duvallii, fig. 482.

CRIOPUS. Poli. Crania, Auct.

CRISTACEA. Lam. The third family of Polythalamous Cephalopoda, Lam. This family is described as including shells of the following characters:—"Multilocular, flattened, nearly reniform; the chambers gradually increasing in length, as they approach the outer arched margin, and appearing to revolve round an eccentric, more or less marginal axis. The Cristacea contain the genera Renulina, Cristellaria, and Orbiculina."

CRISTACEA. Bl. The third family of Polythalamia, Bl. containing the genera Crepidulina, (Cristellaria, Lam.) Oreas and Linthuris.

CRISTARIA. Schum. Dipsas Plicatus, Leach. Anodon tuberculatus, Fer.

CRISTELLARIA. Lam. Crepidulina, Bl. Fam. Cristacea, Lam. and Bl.—Descr. Semidiscoidal, chambered; whorls contiguous, enlarging progressively; spire eccentric, sublateral; septa imperforate. Microscopic.

CRYPTA. Humph. Crepidula, Lam.

CRYPTELLA. Webb. (Κρυπτω, to conceal.) Testacellus Ambiguus of Ferrusac. Published in Sowerby's Genera of Shells as Parmacella calyculata.—Descr. A small patelliform shell, with a very short papillary spire; and the aperture irregularly expanded. Fig. 256. Canary Islands.

CRYPTOCONCHUS. Bl. A genus composed of species of Chiton, the valves of which are covered by the integument, as Chiton porosus of Burrows. Ch. amiculatus of Pallas.

CRYPTODIBRANCHIATA. Bl. The first order of the class Cephalophora, Bl. containing families of molluscous animals destitute of shells.

CRYPTOSTOMA. Bl. Differs from Sigaretus, Lam. principally in the soft parts of the animal. De Blainville remarks that he is acquainted with only two species (from the Indies), which he can with decision refer to the genus, but he thinks that many of the Lamarckian Sigareti may very probably be found to belong to it, as soon as the soft parts shall be known. The species which he figures is Cryptostoma Leachii. (Manuel de Malacologie, pl. 42. fig. 3.)

CTENOCONCHA. Gray. Described as having many characters in common with the Solens, the teeth like Nucula, but the cartilage entirely external. Solenella, Sow.?

CUCULLÆA. Lam. (Cucullus, a hood.) Fam. Arcacea, Lam.—Descr. Sub-quadrate, nearly equivalve, sub-equilateral, deep; hinge rectilinear, with a series of angular teeth, small near the umbones, larger and more oblique towards the extremities; umbones separated by a flat external area, on which the ligament is spread. Anterior muscular impression produced into a sharp-edged plate or ledge, projecting from the side of the shell. Posterior muscular impression flat and indistinct.—Obs. This genus very much resembles Arca in general form, but differs in the oblique, lengthened character of the remote teeth, and in the singularly prominent edge of the muscular impression. China. Fig. 133, C. Auriculifera.

CUCUMIS. Klein. Marginella, Auct.

CULTELLUS. Species of Lutraria, Lam. which have the umbones placed near the extremity of the shell. Ex. L. Solenoides, fig. 78.

CUMA. Humph. Fusus and Fasciolaria, Lam.

CUMINGIA. Sow. Fam. Mactracea, Lam.—Descr. Equivalve, inequilateral, transverse, rounded anteriorly, subrostrated posteriorly. Hinge with a central spoon-shaped cavity in each valve, containing the cartilage; a very small anterior cardinal tooth in each valve; two lateral teeth in one valve, none in the other: muscular impressions two in each valve, distant; palleal impression with a very large posterior sinus.—Obs. The species known at present are found in sand, in the fissures of rocks in Tropical climates. They resemble Erycina in general form and character, but differ in having the internal cartilage placed in a prominent spoon-shaped process, while that of Erycina is contained in a hollow which sinks under the umbones. This genus should be placed near Amphidesma. Cumingia mutica, fig. 87.

CUNEIFORM. (Cuneus, a wedge.) Wedge-shaped, as Donax, fig. 108.

CUNEUS. Megerle. Venus Meroe, Linn. and similar species.

CUNICULA. Sw. A sub-genus of Uniones, thus described:—"Ovate, oblong; bosses thick, but depressed; cardinal teeth moderate. C. planulata, patula, rubiginosa, secura, purpurascens."

CURVED. Arched or bent. Ex. Dentalium, fig. 2.

CURVULA. Rafinesque. A fossil imperfectly described as differing from Pinna, in being inequivalve.

CUVIERIA. Ranz. (Baron Cuvier.) Class, Pteropoda, Lam.—Descr. Thin, transparent, glassy, cylindrical, rounded and inflated at the closed extremity, compressed towards the opening, so as to render it oval. This genus differs from Vaginula in being rounded, instead of pointed, at the lower extremity. Mediterranean. Fig. 223, C. Columella.

CYCLAS. Brug. Fam. Conques Fluviatiles, Lam. Conchacea, Bl.—Descr. Orbicular, thin, subovate, ventricose, sub-equilateral, equivalve; cardinal teeth minute, one more or less complicated in the left valve, two diverging in the right; lateral teeth elongated, compressed, laminar, acute, doubled in the left valve; ligament external; epidermis thin, horny.—Obs. The Cyclades are viviparous, and abound in ditches, ponds, slow streams, &c. in Europe and North America. The genus Pisidium has been separated on account of a difference in the animal, and may be known from Cyclas by being less equilateral, and the anterior side being the longest. Fig. 111, C. Rivicola.

CYCLOBRANCHIATA. Bl. The third order of the second section of Paracephalophora Monoica, Bl. containing no genera of Testaceous Mollusca.

CYCLOCANTHA. Sw. A genus of "Trochidæ," consisting of Turbo stellaris and T. Calcar, and corresponding with the genus Calcar, Montf.

CYCLONASSA. Sw. A genus of "Nassinæ," Sw. consisting of Nassa Neritoidea, and corresponding with the genus Cyclops, Montf.

CYCLOPHORUS. Montf. A generic name proposed for those species of Cyclostoma, Auct. which have an umbilicus. C. Involvulus, fig. 304, would be the type of this genus.

CYCLOPS. Montf. Nassa Neritoidea, Auct. fig. 424.

CYCLOSTOMA. Auct. (κυκλος, cyclos, round; στομα, stoma, mouth.) Fam. Colimacea, Lam. Cricostomata, Bl. A genus of land shells varying in shape from that of Pupa to that of a flat orb; the aperture is generally circular and the peritreme uninterrupted, thickened and sometimes reflected, the operculum is shelly and spiral. Two other genera of land shells are provided with opercula, and consequently might be confounded with this genus. In Helicina, the operculum is concentric and the peritreme is not continuous; while in the small genus hitherto almost unknown of Pupina, the peritreme is not continuous and there is a glassy enamel over the whole of the external surface. In the plates we have represented, C. ferrugineum, fig. 303; C. involvulus, fig. 304.

CYCLOTUS. Guild. A sub-genus of Cyclostoma, consisting of those species which are discoidal, as C. Planorbulum. Fig. 530.

CYLINDER. Montf. Conus textile, Auct. (fig. 461) and other species having a cylindrical form.

CYLINDRELLA. Sw. A genus of the family "Ovulinæ," Sw. composed of cylindrical species of Ovulum? The wood-cut illustrating this genus has the appearance of a Bulla.

CYLINDRICAL. (κυλινδρος, a cylinder.) This like other mathematical terms is used with great latitude by Conchologists, and applied to any shell the sides of which are nearly parallel, with the extremities either rounded, flat, or conical. Ex. Oliva, fig. 457.

CYLLENE. Gray. Fam. Purpurifera, Lam.—Descr. Oval, thick, with a short acute spire; an oval aperture terminating anteriorly in a slight emargination, posteriorly in a short canal; a fold at the lower end of the body whorl; outer lip thick, striated within; angle of the whorls tuberculated.—Obs. This genus of small marine shells resembles Voluta in general character, but differs in having a smooth columella without folds. Recent, Pacific Ocean; Fosil, London clay. Fig. 425.

CYMBA. Brod. (Cymba, a boat or skiff.) Fam. Columellaria, Lam.—Descr. Smooth, ventricose, with a very short, mammillated, rude spire; and a very large, wide aperture, terminated anteriorly in a deep emargination; posteriorly in a flat ledge, which separates the outer lip from the body whorl; columella with three or four oblique, laminar, projecting folds, terminating in a point; outer lip thin, with its edge sharp; epidermis smooth, brown, covered partly or entirely by the glassy enamel, which, commencing with the outer lip, spreads over the body of the shell.—Obs. These very elegant shells, found in Africa, are distinguished from the true Volutes by the shapeless, mammillated apex of the short spire, by the large size of the aperture, and by the horizontal ledge which separates the outer lip from the body whorl. The genus Melo, also separated by Mr. Broderip from the Volutes, agrees with Cymba in some respects, but differs in the regularity of the spire. Fig. 434, C. Porcina.

CYMBIOLA. Sw. The generic name for a group of Volutes, described as "armed with spinous tubercules, sometimes smooth, but never ribbed; spiral whorls gradually diminishing in size, but not distorted; apex thick and obtuse; pillar with four plaits." Mr. Swainson remarks that this genus is chiefly distinguished by the obtuse, but not irregular spire. The typical species are stated to be V. Rutila and V. Vespertilio, fig. 433. Tropical.

CYMBULIA. (Dim. from Cymba.) Fam. Pteropoda, Lam. An extremely light, cartilaginous covering of a molluscous animal, so named from its similarity in shape to a boat. We mention it here on account of its similarity to the shelly or glassy covering of other Pteropods, to which, although membranaceous, it is evidently analogous. The Cymbuliæ are found in the Mediterranean.

CYPRÆA. Auct. Fam. Enroulées, Lam. Angyostomata, Bl.—Descr. Oval or oblong, ventricose, convolute, covered by an enamel, generally smooth and shining. Spire short, nearly hid. Aperture long, narrow, terminating in a short canal at both extremities. Outer lip dentated, thickened, inflected. Inner lip dentated, thickened, reflected over part of the body whorl.—Obs. These shells are so distinguished by the two rows of teeth arranged on each side of the aperture; the thickened front formed by the inner and outer lips; and the enamel deposited over the back of the shell from the mantle of the animal which envelopes it, that there is no danger of confounding them with any other genus, except in a young state. Before they have arrived at the full growth, the front is not thickened, and the outer lip is thin, not inflected, nor are the teeth formed. In this state the shell resembles, in some degree, an Oliva. Some species are striated, ribbed, or tuberculated, but the generality are smooth. Most species belong to tropical climates, only one to Great Britain. The C. Moneta is current as money in some parts of Africa, and many species are worn as ornaments by the South Sea Islanders. The colouring in most species is exceedingly rich, and arranged in every variety of spots, patches, rings, lines, bands and clouds. The species most esteemed by collectors are C. Mappa, C. Testudinaria, C. Pustulata, C. Aurora, C. Princeps, of which only two specimens are known, C. Leucodon, &c. See also Cypræovulum, Trivea and Luponia. The fossil species are principally from the Calc-grossier, the London Clay, Crag, &c. Fig. 445 to 450. The latest revision of this genus has been effected by Mr. G. B. Sowerby, sen., who has published a complete catalogue in his son's Conchological Illustrations. This catalogue enumerates 130 species, the whole of which are figured in parts 1 to 8, 101 to 131 of the above mentioned work.

CYPRÆCASSIS. Stutch. (Cypræa and Cassis.)—Descr. Shell, when young, striated, reticulated, or tuberculated; outer lip simple: when mature, outer lip involute and toothed; columellar lip also toothed; aperture straight, anteriorly terminated by a recurved canal, posteriorly by a shallow channel. Animal with the mantle bilobed; operculum none.—Obs. The reasons given for separating this genus from Cassis, are, 1st, That the shells of the latter have an operculum, while those of the proposed genus have none. 2nd, That the Cypræcassides do not form a complete, thickened lip, before the full period of their growth, like the Cassides. 3rd, That the Cypræcassides have no epidermis. The species mentioned as probably belonging to Cypræcassis are C. rufa, the type; C. coarctata, and C. Testiculus, Auct. The establishment of this genus has been opposed on the ground that indications of epidermis are discoverable in some specimens of C. rufa; that some specimens of the same species and Testiculus have been examined, and found to have formed slightly thickened and dentulated outer lips at very early periods of growth, while many of the other Cassides are destitute of varices, and that an operculum of C. coarctata was brought to this country by Mr. Cuming. It is probable, however, that an increased knowledge of facts might go far to establish the separation. C. Testiculus, fig. 412.

CYPRÆADIA. Sw. A genus of the family "Cypræidæ," Sw. thus described:—"Cypræform; the base contracted; the body whorl not flattened beneath; shell cancellated; aperture of equal breadth throughout; a few thickened, short teeth on the pillar; lip at the base, which is not internally concave. C. cancellata, Sw. Fossil only, differing from Trivea in its contracted base, in the inequality of its aperture, and the equal convexity of the inner lip within." (Sw. Lardn. Cyclop. Malac. p. 325.) Cyprædia, fig. 564.

CYPRÆLA. Sw. A genus formed for the reception of Ovulum verrucosum, Auct. which has a circular depression at each extremity. It is the same as the genus Calpurnus of De Montfort. Ovulum verrucosum, fig. 441.

CYPRÆOVULUM. Gray. A genus of Cypræidæ thus described, "shell like a cowry, but front end of columella covered with regular cross-ribs, like the rest of the base, internally produced into an acute toothed ridge. Shell pear-shaped, cross-ridged." C. capense, fig. 444. South Africa.

CYPRICARDIA. Lam. Fam. Cardiacea, Lam.—Descr. Equivalve, inequilateral, subquadrate, transversely elongated, with the anterior side very short; hinge with three cardinal teeth and one remote lateral tooth in each valve; muscular impressions two in each valve; ligament external.—Obs. This genus is distinguished from Cardita by the three cardinal teeth. The mollusca of this genus are marine. C. angulata, fig. 125. Pacific Ocean.

CYPRINA. Lam. Fam. "Conques Marines," or Marine Conchacea.—Descr. Equivalve, inequilateral, sub-orbicular; umbones curved obliquely; hinge with three diverging cardinal and one remote lateral teeth in each valve; ligament external; muscular impressions two in each valve; palleal impression having a slight posterior sinus; epidermis thick, rough brown.—Obs. The Cyprinæ belong to the Northern hemisphere. The recent species are not numerous. Fossil species are found in the tertiary deposits. Cyprina may be known from Venus by the remote lateral tooth and the thick epidermis. C. vulgaris, fig. 116.

CYRENA. Auct. Fam. Fluviatile Conchaceæ, Lam. Conchacea, Bl—Descr. Suborbicular, equivalve, inequilateral, ventricose, corroded at the umbones, thick, covered with a thick epidermis; hinge with three cardinal and two remote lateral teeth in each valve. Muscular impressions two in each valve; palleal impression not sinuated.—Obs. This genus is distinguished from Venus, Cytherea and Cyprina, by having two remote lateral teeth; and from Cyclas by the thickness of the shell. This genus is mostly fluviatile; the recent species are tropical, and the fossil are found in the newest formations. Fig. 113, C. fuscata.

CYRENELLA. Desh. See Cyrenoides.

CYRENOIDES. Joannis. Cyrenella, Desh. Fam. Conques Fluviatiles, Lam.—Descr. Equivalve, subequilateral, ventricose, thin, covered with a reddish brown epidermis, corroded at the umbones, with a slight posterior fold. Hinge thin, with three diverging cardinal teeth in each valve, and a very slight posterior fold in the right valve. Ligament not very tumid.—Obs. This fresh-water shell differs from Cyclas and Cyrena in the want of lateral teeth, and from the latter in the thinness of the shell. Fig. 114.

CYRTIA. Dalman. (Κυρτος, curtos, gibbose.) Fam. Brachiopoda, Lam.—Descr. "Hinge rectilinear; with the back elevated into a semicone or half-pyramid, the cardinal side perpendicularly plane."—Obs. This genus of fossil Brachiopoda forms part of the genus Spirifer, Sow. C. exporrecta, (Anomites exporrecta, Nonnull.) fig. 204.

CYTHEREA. Lam. Fam. "Conques Marines," Lam.—Descr. Equivalve, inæquilateral, oval, lenticular, or sub-trigonal; hinge with two or more short, diverging cardinal teeth, and one anterior approximate lateral tooth in each valve.—Obs. The Cythereæ are distinguished from the Veneres by the lateral tooth. C. Meretrix, fig. 117, and 117, a. b. c. d.

DACTYLUS. Humph. Marginella, Auct.

DARACIA. Gray. A subgenus of Pyrgoma, including a species which is remarkable for the irregularity of its form. It grows upon a species of Monticularia, and the margin takes the shape of the lobes by which it is surrounded. The aperture is large, and completely closed by the operculum. Daracia (Pyrgoma) Monticulariæ, fig. 489, 490.

DATE. A common name given to shells of the genus Pholas, on account of their cylindrical form and consequent resemblance to the fruit. For the same reason the name Pholas Dactylus has been given by Naturalists to the species which we represent, fig. 66.

DEAD SHELL. A term used among collectors to signify that the shell has been exposed on the sea-shore after the animal has ceased to live. A shell in this condition is worn down by attrition, and loses its beauty and brilliancy of colouring by being subject to the action of salt water. A dead shell may be known by a certain hoary whiteness spread over its surface.

DECACERA. Bl. The second family of the order Cryptodibranchiata, Bl. containing the genera Calmar and Sepia, which have no shells.

DECADOPECTEN. Rüppell. Pecten Plica, Linn. Fig. 172, having a plicated hinge.

DECOLLATED. (Decollari, to be beheaded.) The apex or nucleus of some shells being composed of a more fragile substance than the rest, has a tendency to fall off. The reason of this probably is that the animal withdrawing from that part, leaves it unprotected. When it falls off, the hole is stopped up by a septum filling the cavity of the volution, so as to exclude the air: the shell is then said to be decollated. Ex. Bulinus decollatus, fig. 289.

DECUSSATED. Intersected by striæ crossing each other. Ex. Rissoa, fig. 346.

DELPHINULA. Montf. (Delphinus, a dolphin.) Fam. Scalariens, Lam. Cricostomata, Bl.—Descr. Orbicular, depressed, thick, rugose; whorls few, angulated, branched at the angles; aperture pearly, rounded or sub-quadrate; peritreme continuous, thickened; operculum horny, composed of numerous whorls.—Obs. Several fossil species are found in the tertiary deposits. D. laciniata, fig. 352. Recent species belong to tropical climates.

DELTHYRIS. Dalman. Fam. Brachiopoda, Lam.—Descr. Hinge more or less rounded, with distant umbones; both valves convex; with the umbo of the largest rostrated and deltoid, with a hollow. This genus forms part of the genus Spirifer, Sow. Fig. 205. D. Plycotes, Dalman.

DELTOID. (Δ, delta.) Triangular.

DENDOSTREA. Sw. (Δενδρον, dendron, tree; οστρεον, ostreon, oyster.) Ostrea Crista-galli, and other species which are attached to stems of sea-weed and corallines, by means of arms thrown out from the inner surface of the lower valve. Fig. 181, Ostrea Folium.

DENTALIUM. Auct. (Dens, a tooth.) Fam. Maldania, Lam. Order, Cirrobranchiata, Bl.—Descr. Tubular, arched, increasing in size towards the anterior extremity, open at both ends; small aperture sometimes having a lateral fissure; large aperture round; external surface ribbed, striated or smooth.—Obs. The well known shells composing this genus are shaped very much like an elephant's tusk, and are not liable to be confounded with any other genus. The fossil species are sometimes termed Dentalithes, from dens, a tooth, and lithos, a stone. The Dentalia, being true molluscs, are not rightly placed among the Annelides. Fig. 2, D. octogonum. Found on sandy shores in most climates.

DENTATED. Having teeth or raised points.

DENTICULATED. (Denticulatus, Lat.) Having little teeth or raised points.

DEPRESSED. Flattened, pressed down, as the spires of some shells.

DEXTRAL Spiral Shells. Place the point of a spiral shell towards the eye, with its mouth downwards; if, as in most instances, the aperture be on the right side of the axis, it is a dextral shell, if otherwise, it is sinistral or reversed. Balea (fig. 296), and Clausilia (fig. 295), are examples of reversed shells.

DEXTRAL Valve. Take a bivalve shell closed, place it before the eye, with the umbones uppermost, and the posterior side, which may be known by the ligament towards the observer, whose right side will then correspond with the right valve of the shell.

DIADEMA. Ranz. Coronula Diadema, Auct. fig. 17.

DIANCHORA. Sow. Fam. Pectinides, Lam. Order, Palliobranchiata, Bl.—Descr. Inequivalve, attached, oblique, subtriangular; attached valve, having an opening in the place of the umbo; the other valve auriculated, with an obtuse umbo; hinge without teeth.—Obs. The green sand fossils contained in this genus differ from Plagiostoma in being attached. Fig. 175, D. striata.

DIAPHANOUS. (Δια, dia, through; φαινω, phaino, to shine.) Transparent.

DIAPHRAGM, (διαφραγμα, a partition.) This term is applied to the septa, by which the chambers of multilocular and other shells are divided from each other.

DICERAS. Lam. (Δις, dis, double; Κερας, ceras, horn.) Fam. Chamacea, Bl. and Lam.—Descr. Inequilateral, inequivalve, attached by the point of the umbo of the larger valve; umbones prominent, spirally twisted and grooved; hinge with one large thick tooth in the larger valve; muscular impressions, two in each valve.—Obs. The prominent spiral umbones, which give rise to the name of this genus, with the circumstance of its being attached by the point of one of them, is sufficient to distinguish it from any other, although it appears to approach Isocardia in some characters. In others it will be found still more nearly to resemble Chama. In fact, from being attached and irregular, the shells composing this genus have been considered as Chamæ with produced umbones. The singular fossil shells composing this genus, are found in granular limestone, near Geneva and in Normandy. Fig. 154, D. perversum.

DIDONTA. Schum. Saxicava. Auct.

DIFFUSE. (Diffundo, to spread out, to dilate.) A term applied to the aperture of a univalve shell, when it is spread out or widened into a flat surface, or digitations. Alated is another term used to express the same character. Thus, the shells belonging to the family of Alatæ, in the system of Lamarck, are diffuse in the outer lip. Fig. 402 to 406.

DIGITATED. (Digitus, finger.) Branched out in long points, as Ricinula, fig. 413.

DILATED. Expanded, spread. This term has the same application as diffuse and alated, explained above. The outer lip of Rostellaria Columbaria, fig. 403 (Hippochrenes, Montf.), will serve as an example.

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

DIMYARIA. (Δις, dis, double; μυον, myon, muscle.) The first order of Conchifera, Lam. including those molluscs which have two adductor muscles, and consequently two muscular impressions in each valve. The Conchifera Dimyaria are divided into Crassipedes, Tenuipedes, Lamellipedes, and Ambiguæ, fig. 44 to 155.

DIOICA. Bl. The first division of the class Paracephalophora, Bl. It is divided into the orders Siphonobranchiata and Asiphonibranchiata, Bl.

DIPLODON. Spix. Hyria Syrmatophora, Lam. fig. 144, and Unio multistriatus, Lea, are doubtfully quoted by Lea as belonging to this apparently ill-defined genus of Nayades.

DIPSAS. Leach. A genus or sub-genus of Nayades, the distinctive character of which is "having a linear tooth under the dorsal edge." D. plicatus, fig. 142.

DISCINA. Lam. Orbicula, Auct.

DISCODOMA. Sw. A sub-genus of Lucerninæ, Sw. (Helix), thus described, "teeth none; aperture angulated; the inner lip nearly obsolete; the outer only slightly thickened; margin carinated."

DISCOIDAL. (Discus, a circular plane.) A spiral shell is said to be discoidal, when the whorls are so horizontally convolute as to form a flattened spire. Ex. Planorbis, fig. 311. Orbulites Discus, fig. 479.

DISCOLITES. Montf. A genus of microscopic Foraminifera.

DISCONTINUOUS. Interrupted. Ex. The siphon of Nautilus is discontinuous, i. e. its termination in one chamber does not reach to its commencement in the next. The varices of Triton, occurring in different parts of the whorls, do not form the continuous ridges which characterize the generality of the Ranellæ.

DISCORBITES. Lam. A genus of microscopic Foraminifera.

DISTANT. The teeth on the hinge of a bivalve shell are said to be distant when they are remote from the umbones.

DIVARICATED. Diverging, meeting in a point, as the teeth on the hinge of Placuna, fig. 184.

DOLABELLA. Lam. (Dim. from Dolabra, a hatchet.) Fam. Aplysiacea, Lam. and Bl.—Descr. Hatchet-shaped, arched, covered with a horny epidermis; posteriorly attenuated, thickened, sub-spiral, anteriorly plane, broad, thin; posterior margin reflected.—Obs. The two or three species of Dolabella known are inhabitants of the Indian Ocean. They were placed by Linnæus in his very convenient genus Bulla, under the name B. dubia. Fig. 255, Dolabella Rumphii.

DOLIUM. D'Argenville. (a tun.) Fam. Purpurifera, Lam. Entomostomata, Bl.—Descr. Thin, ventricose, oval, or globular, with a short spire; large aperture terminating in a reflected canal, and spirally ribbed or grooved external surface; outer lip crenated; inner lip reflected over part of the body whorl, which terminates in a tumid varix; epidermis light, horny. Mediterranean and East Indian.—Obs. This genus is distinguished from Cassis by the outer lip, which is not reflected. The species which are not so rotund as the others, as D. Perdix, Auct. have been separated under the name Perdix, as generic. Fig. 420, Dolium Maculatum.

DONAX. Auct. Fam. Nymphacea, Lam. Conchacea, Bl.—Descr. Equivalve, inequilateral, trigonal, with the anterior side short, straight, plane; the posterior side elongated, drawn to a narrow, rounded termination; hinge with two cardinal teeth in one valve, one in the other, and one or two, more or less remote lateral teeth; ligament external; muscular impressions two in each valve; palleal impression sinuated posteriorly.—Obs. The Capsæ have not the crenated margins, the short anterior side, and the distinct lateral teeth, which characterize the Donaces. Some species of Erycina resemble Donax in general form, but are at once distinguished by the ligamentary pit in the hinge. Sandy shores in all climates. Fig. 108, D. cuneatus.

DORSAL. A dorsal shell is one placed upon the back of the animal. The dorsal margin of a bivalve shell is that on which the hinge is placed; the opposite margins are termed ventral. The dorsal surface of a spiral univalve is that which is seen when the aperture is turned from the observer. The dorsal valve is the uppermost in Brachiopodous bivalves. The dorsal part of a symmetrical convolute univalve, such as the Nautilus and Ammonite is that part of the whorls which is at the greatest distance from the spire, that is, the outer part of the whorls. Thus the situation of the siphon is said to be dorsal when it pierces the septum near the outer edge of the whorls. The dorsal part of symmetrical conical univalves, such as Patella, is the upper part, on which the apex is placed.

DORSALIA. Lam. (Dorsum, the back.) The first family of the order Annelides Sedentaria, Lam. containing the genera Arenicola, not a shell, and Siliquaria, fig. 1, which is now considered as a true mollusc, and placed next to Vermetus.

DOSINA. Schum. Venus Verrucosa, Casina, and similar species. Fig. 119, a.

DREISSINA. Mytilus Polymorphus. Auct. fig. 159. This genus differs from Mytilus principally in the characters of the animal. The shell is characterized by a small septiform plate under the hinge within. Fluviatile, Europe and Africa.

EBURNA. Lam. (Eburneus, ivory.) Fam. Purpurifera, Lam. Entomostomata, Bl.—Descr. Oval, thick, smooth, turrited, umbilicated; spire angulated, acute, nearly as long as the aperture; aperture oval, terminating anteriorly in a canal, posteriorly in a groove; outer lip slightly thickened with an anterior notch, which terminates in a spiral fold surrounding the body whorl; umbilicus generally covered by the thickened columellar lip.—Obs. The beautiful shells called ivory shells, which originally constituted part of this genus, are now placed in the genus Ancillaria by authors. They differ from the present genus Eburna, in having the sutures of the spire covered with a polished enamel. (A. glabrata, fig. 455.) The Eburnæ resemble in some respects the genus Buccinum, but a glance at the figure will enable the reader to distinguish a true Eburna from all other shells. Fig. 426 is Eburna Zeylanica. A catalogue of 9 species is given in part 20 of the Conchological Illustrations published by the Author, accompanied by figures of several species.

ECHIDNIS. Montf. Described as a straight, chambered, annulated, fossil shell, computed from the extremely gradual increase in diameter of the fragments to be at least sixteen feet long. Found in marble from the Pyrenees.

ECHINELLA. Sw. A sub-genus of Monodonta. Sw. Malac. page 352.

EFFUSE. (effundo, to pour out.) The aperture of an univalve shell is said to be effuse when there is a notch in the margin which would suffer a liquid to escape, and thus prevent it being filled to the brim.

EGEON. Montf. A genus of microscopic Foraminifera.

EGERIA. Lea. (Contrib. to Geol. p. 49, pl. 1.) A genus of fossil bivalves, described as very variable in form, with or without lateral teeth, sometimes a crenated margin, &c. The only certain characters appear to be that they have two diverging cardinal teeth in each valve, one of which is bifid; and an external ligament. Lea states that the Egeriæ should be placed between the Sanguinolariæ and the Psammobiæ, which two latter genera have been united by Sowerby. Fig. 103, E. Triangulata, from the tertiary formation of Alabama.

ELENCHUS. Humph. A genus composed of Trochus Iris, Auct. and other similarly formed species. It is the same as Cantharidus of Montfort.

ELEPHANT'S TUSK. The common name given by dealers to shells of the genus Dentalium. Ex. D. octogonum, fig. 2.

ELEVATED. A term which is applied by some conchological writers to the spire of an univalve shell when it consists of numerous whorls drawn out into a telescopic form. Other authors use the term elongated, or the more simple one 'long,' to express the degree of elevation.

ELISMA. Leach. A sub-genus of Bulinus. B. acutus, Auct. Gray, Turton, p. 185.

ELLIPSOLITHES. Montf. (Ελλειψις, ellipsis, oval; λιθος, lithos, stone.) A genus composed of Ammonites, which instead of being regularly orbicular, take an elliptical or oval form. This character appears to be accidental, as some individuals of the same species, both of Nautilus and Ammonites, are round, while others are compressed into an oval form.

ELLIPSOSTOMATA. Bl. (Ελλειψις, ellipsis, oval; στωμα, mouth.) The third family of the class Asiphonibranchiata, Bl. The shells of this family are described as of various forms, generally smooth; the aperture longitudinally or transversely oval, completely closed by a horny or shelly operculum. This family contains the genera Rissoa, Phasianella, Ampullaria, Helicina, and Pleuroceras.

ELLIPTICAL. (Ελλειψις, ellipsis.) Oval. Applied to any shell or part of a shell, having that form.

ELMINEUS. Leach. Order, Sessile Cirripedes, Lam.—Descr. Four unequal valves, arranged circularly side by side, forming a quadrate cone; aperture large, sub-quadrate, irregular; operculum composed of four valves, in pairs.—Obs. This genus differs from Conia in the structure of the shell, the latter being porous. Fig. 22, Elmineus Leachii.

ELPHIDIUM. Montf. (Conch. Syst. t. 1. p. 15.) A genus of microscopic Foraminifera.

EMARGINATED. (e, out; margo, border.) Notched or hollowed out. Applied to the edges or margins of shells, when instead of being level they are hollowed out, as the outer lip of Oliva, fig. 457, at the base, and the ventral margins of some bivalves.

EMARGINULA. Lam. (e, out; margo, border.) Fam. Calyptracea, Lam. Branchifera, Bl.—Descr. Patelliform, oblong or oval; anterior margin notched or emarginated; apex posteriorly inclined; muscular impressions wide.—Obs. Emarginula elongata, of some Authors, Parmophorus of De Blainville is commonly called the Duck's bill limpet, from its shape. The Emarginulæ may be known from Patellæ and other neighbouring genera, by the notch or slit in the anterior edge. In the genus Rimula, Defr. fig. 243, this slit is near the apex, and does not reach the margin. Recent species occur in all climates, but are not numerous. Fossil species are still more rare, occurring in the Calc-grossièr, Crag and Oolite. E. fissurata, fig. 241.

ENA. Leach. A sub-genus of Bulinus. B. Lackhamensis. Mont.

ENDOSIPHONITES. A genus composed of Ammonites, having the siphon close to the body whorl, fig. 476.

ENDOTOMA. Rafinesque. A genus of microscopic Foraminifera.

ENROULEES. Lam. See Convolutæ.

ENSATELLA. Sw. A genus consisting of Solen ensis, Auct. fig. 60, and other species similarly curved. Genus Ensis, Schum.

ENSIS. Schum. Solen ensis, Auct. and similar species.

ENTALIS. Defr. Dentalium duplicatum, Bl. Pharetrium, König. This genus is described as a small tube, within a larger one, the smaller extremity of the inner tube projecting beyond that of the outer one. Deshayes, who describes this genus, expresses a conviction that the soft parts of the animal must be entirely different from those of the animal of Dentalium. The genus Pharetrium, as described by König in his "Icones Fossilium Sectiles," is evidently identical with Entalis. It is placed by him in the family of Pteropoda, but being a fossil shell, there is some difficulty in finding its place in the system. See plates, fig. 3.

ENTELLITES. Fischer. A genus composed of species of Terebratula, Spirifer, and Productus, Auct. having the hinge large and the umbones short. Orthis? Dalman.

ENTIRE. (Integra.) Not interrupted, not emarginated. The peritrême of a univalve shell is said to be entire when not interrupted by canals or by the body whorl. Ex. Cyclostoma, fig. 304. The palleal impression is entire, when continued without interruption, or without a sinus.

ENTOMOSTOMATA. Bl. The second family of the order Siphonibranchiata, Bl. The shells of this family are described as differing but little from those contained in the family of Siphonostomata of the same author, both with regard to the soft parts, and their testaceous covering. This family partly answers to the Purpuriferæ in the system of Lamarck, and contains the genera Subula, Cerithium, Melanopsis, Planaxis, Terebra, Eburna, Buccinum, Harpa, Dolium, Cassidaria, Cassis, Ricinula, Cancellaria, Purpura, Concholepas.

EOLIDES. Montf. A genus of microscopic Foraminifera.

EPIDERMIS. (Επι, epi, over or upon; δερμα, derma, skin.) The fibrous, horny, external coating of shells, called by the French, "Drap marin," or marine cloth. Lamarck objects to the name Epidermis because he does not consider the substance as answering to the cuticle or scarf skin of the human body, but more analogous to the nails and hair. Gray calls it the Periostracum, from the membranous skin covering the bones of quadrupeds.

EPIPHRAGM. The membranaceous or calcareous substance by which some species of molluscs close the aperture of the shell, when they retire within it to hibernate. When the animal wishes to come forth from his hiding-place, again to breathe the air, the edges of the Epiphragm are detached by a chemical process, so that it drops off. The name Hibernaculum has also been given to this covering. It must not be confounded with the operculum, which is a permanent portion of the shell, and is used as a door, fitted to the foot of the animal and moved at will to open or close the aperture of the shell, whereas the Epiphragm is produced for the occasion from a mucous secretion of the animal and dissolved at the edges when no longer wanted, when it drops off.

EPISTYLA. Sw. A subgenus of the genus Helix. E. conical. Sw. Helix Epistylium, fig. 281.

EPONIDES. Montf. A genus of microscopic Foraminifera.

EQUILATERAL. (Æquus, equal; latus, side.) Equal-sided. A term applied to bivalve shells, when a line drawn down perpendicularly from the apex would divide the shell into two equal parts. Ex. Pectunculus pilosus, fig. 134.

EQUIVALVE. (Æquus, equal; valva, a valve.) A term applied to a bivalve shell when the valves are equal to each other in dimensions.

ERATO. Risso. Fam. Convolutæ, Lam.—Descr. Ovate, more or less angulated, smooth or granulated, with a dorsal scar; spire short; aperture large, angulated, emarginated; columella slightly crenated; 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. (Γαστηρ, gaster, belly; πους, ποδος, 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, those which breath air, or land molluscs; and Hydrobranchiata, or those which breath water, marine or fresh-water molluscs. Fig. 227 to 263.

GASTRANEA. Schum.? Corbula, Auct.

GASTROCHÆNA. Speng. (Γαστηρ, gaster, belly; χαινο, chaino, gape.) Fam. Pholadaria, Lam. Pyloridea, Bl.—Descr. Equivalve, regular, inequilateral, with a wide, oblique, ventral hiatus, enclosed in a curved pyriform tube. Differing from Galeomma in being a free, oblique shell; from Fistulana, in the oval shape of the valves, and the curve of the tube; from Aspergillum and Clavagella, in both valves being free.—Obs. The Gastrochænæ are found in the hollows of massive shells or other marine substances. Fig. 62, G. Modiolina.

GASTROPLAX. Bl. Umbrella, Lam. De Blainville described this genus from a specimen in which the shell had been, probably by accident, placed upon the under part of the animal, and not discovering his error until afterwards, gave it the above name.

GEOMITRA. Sw. A sub-genus of Geotrochus, Sw. founded on a trochiform species of Helix, with coronated nodules on the whorls. Helix bicarinata, Sow. Zool. Journ. 1, pl. 3, fig. 7. Sw. page 166 and 332.

GEOPHONUS. Montf. Conch. Syst. t. 1, p. 19. A genus of microscopic Foraminifera.

GEOTROCHUS. Sw. Helix pileus, Auct. (fig. 278,) and other trochiform species. Divided into the sub-genera Pithohelix, Geotrochus, Hemitrochus, Gonidormus, and Geomitra. Sw. p. 165 and 166, described at page 331.

GEOVULA. Sw. A sub-genus of Melampus (Auricula), consisting of oval species, resembling Auricula Midæ, fig. 297.

GERVILLIA. Defr. Fam. Margaritacea, Bl. Malleacea, Lam.—Descr. Equivalve, oblong, oblique; hinge long, straight, having small, irregular, transverse ligamentary pits.—Obs. This genus of fossil shells, found at various geological periods, from the Lias to the Baculite limestone in Normandy, is now extinct. In general form it resembles Avicula, but in the hinge it approaches Perna. Fig. 169, G. Avicularis.

GIBERULA. Sw. A genus separated from Marginella, Auct. and thus described, "sub-oval; spire slightly prominent; top of the outer lip dilated and gibbous; base of the inner lip with plaits; inner lip broad, spreading. G. Zonata. Enc. Méth. 374, f. 6."

GIBBOSE or GIBBOUS. (Gibbosus.) Bunched out, embossed, having a lump or swelling of any kind. Ex. Bulinus Lyonetianus, (fig. 284.) named Gibbus by De Montfort. Ovulum gibbosum.

GIBBUS. Montf. Bulinus Lyonetianus, Lam. Pupa, Bl. fig. 284.

GIOENIA. A name given in the Encyclopédie Méthodique, to the plates of the stomach of Bulla Lignaria.

GLABELLA. Sw. Marginella Glabella (fig. 437), Goodallii, Auct. and similar species.

GLANDINA. Schum. Polyphemus, Montf.

GLANDIOLUS. Montf. A genus of microscopic Foraminifera.

GLAUCONOME. Gray. Fam. Solenacea, Lam.—Descr. Oblong or oval, transverse, slightly ventricose, equivalve, inequilateral; margins close, rounded anteriorly, somewhat acuminated posteriorly; hinge teeth, three in each valve, of which the central in one, and the posterior in the other, are bifid; muscular impressions anterior, elongated, marginal; posterior sub-quadrate; palleal impression, having a long sinus; ligament oblong, external; epidermis thin, horny, green, folded over the margins.—Obs. This shell, of which only one species is known, inhabits some of the rivers in China. C. Chinensis, fig. 64.

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

GLOBOSE. (Globosus.) Rounded like a globe or ball, as the species of Helix, represented in fig. 268.

GLOBULARIA. Sw. A sub-genus of Natica, consisting of globose species. (Sw. p. 345.) Ex. N. Lineata, fig. 328.

GLOBULUS. Sow. Min. Con. Ampullaria, Auct.

GLYCIMERIS. Lam. Fam. Solenacea, Lam. Pyloridea, Bl.—Descr. Equivalve, transverse, oblong, thick, compressed, gaping at both extremities; hinge callous, without teeth; ligament large, external, prominent; epidermis thick, black, horny, folded over the margins; muscular impressions two, distant, running into the irregular palleal impression which unites them.—Obs. But few species of this singular genus are known; Lamarck describes two species from the Northern Seas. Blainville is of opinion that they belong to the family of the Nayades. Fig. 67, G. Siliqua.

GNATHODON. Gray. (Γναθος, gnathos, jaw-bone; οδος, οδοντος, odontos, tooth.) Fam. Mactracea, Lam.—Descr. Ovate, posteriorly angulated, equivalve, thick, ventricose, inequilateral, covered with a greenish brown epidermis; umbo distant, prominent; hinge having in one valve a sharp, angular, notched, cardinal tooth, and two lateral teeth, the posterior of which is elongated, and the anterior angulated, tortuous, shaped like a jaw-bone; in the other valve, two cardinal and two lateral teeth, the anterior of which is wedge-shaped; ligament internal, cuneiform, placed in a deep cardinal pit proceeding from the umbones; muscular impressions two; palleal impression having a slight sinus.—Obs. Only one species is known, G. cuneatus, fig. 83, from New Orleans. It is known from all other shells by the character of the hinge.

GONIATITES. De Haan. A genus composed of species of Ammonites, Auct. in which the last whorl covers the spire and the sinuations of the septa are angulated. Fig. 480, G. striatus.

GONIDOMUS. Sw. A sub-genus of Geotrochus, Sw. Pupa pagodus, Auct. Sw. p. 332.

GONIOSTOMA. Sw. A sub-genus of Bulimus, thus described, "spire elongated, of few whorls; aperture contracted at each end; lips margined; the pillar curving inwards; the base slightly notched. G. erubescens, Sw. Zool. Journ. i. pl. 5, f. 2." Sw. p. 335.

GONIOSTOMATÆ. Bl. A family belonging to the order Asiphonibranchiata, Bl. containing the genera Solarium and Trochus.

GONOSPIRA. Sw. A sub-genus of Pupa, thus described, "spire perfectly cylindrical, of equal thickness, the tip obtuse, with the whorls large; aperture oval; lips thickened; pillar with or without a plait. G. polanga, Desh. Lesson, Voy. pl. 8, f. 8." Sw. p. 333.

GRANULATED. (Granum, a grain.) Covered with minute grains, rough. The granulated lip of Oniscia, (fig. 409) will serve as an example.

GRATELOUPIA. Moulins. Fam. Nymphacea, Lam.—Descr. Equivalve, inequilateral, sub-cuneiform, rounded anteriorly, sub-rostrated posteriorly; hinge with three cardinal teeth, a series of five or six irregular, small, diverging teeth behind the umbones, and one lateral anterior tooth in each valve; ligament external; muscular impressions two; palleal impression sinuated posteriorly.—Obs. This genus (Donax irregularis, Bast.) is only known in a fossil state. Fig. 102, G. Moulinsii.

GRYPHÆA. Lam. (From Gryps, a griffin.) Fam. Ostracea, Lam.—Descr. Inequivalve, free; lower valve large, concave; with the umbo prominent, incurved; upper valve small, flat, opercular; hinge toothless, with a curved, depressed area; one muscular impression.—Obs. These shells, which approach the Oysters, are of a more regular form, and are remarkable for the curved, produced beak of the lower valve. They are only known in a fossil state, belonging to the more ancient strata. Fig. 182, G. incurva. The recent species mentioned by Lamarck is not a true Gryphæa.

GYMNOLEPAS. A generic name used by De Blainville to include Otion and Cineras, Leach.

GYMNOSOMATA. Bl. The second family of the order Aporobranchiata, in the system of De Blainville. The animals belonging to this family are destitute of shells.

GYPIDEA. Dalman. A genus of Brachiopoda, thus described, "Larger valve with the umbo rostrated, remote from the hinge; with the canal large, deltoid; bilocular within." Pentamerus, Sow. Fig. 210. 211, G. Conchidium, copied from Dalman.

GYROGONA. Lam. A genus of microscopic Foraminifera.

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

HALIOTIDÆ. Sw. A sub-genus of Calyptræa. Calyptræa dilatata. Sowerby's Genera of Shells, fig. 9.

HALIOTIS. Auct. (αλς, als, sea; ους, ωτος, otos, ear.) Fam. Macrostomata, Lam. Otides, Bl.—Descr. Auriform, broad, depressed, pearly within, rough, costated, tuberculated without; spire short, flat, consisting of one or two whorls; aperture wide; ovate; columella laminar, flat, oblique; a spiral series of perforations running along the dorsal margin.—Obs. The splendid shells belonging to this genus are remarkable for the pearly iridescence of the inner surface, and the row of holes following the course of the spire. The soft parts are eaten in Guernsey and Jersey, and reckoned delicious. They belong to temperate and tropical climates. Fig. 338, H. rubra. 339, Padollus, Montf.

HALIOTOID. (Haliotis and ειδος, eidos, form.) Ear-shaped.

HAMIFORM. (Hamus, a hook.) Curved at the extremity.

HAMITES. Parkinson. (Hamus, a hook.) Fam. Ammonacea, Lam.—Descr. Elongated, cylindrical, chambered, recurved at the smaller extremity, annulated; septa lobed and sinuated.—Obs. This remarkable fossil from the Baculite limestone in Normandy, differs from Baculites in being curved at one extremity, a circumstance from which its name is derived. Some small species are found in Chalk-Marle, Folkstone. Fig. 484*. H. cylindricus.

HARPA. Brug. (Harpa, a harp.) Fam. Purpurifera, Lam. Entomostomata, Bl.—Descr. Oval, ventricose, longitudinally and regularly costated; spire short, with rounded, dome-like whorls; aperture wide, emarginated; outer lip thickened, reflected, composing the last costa or rib; inner lip polished, spread over part of the body whorl, terminating in a point.—Obs. This beautiful genus of shells is so clearly defined by the regular, longitudinal ribs that adorn the external surface, suggesting the idea of a stringed instrument, that there is no danger of confounding it with any other. H. multicostata, (Buccinum costatum, Linn.) and H. ventricosa, are among the most elegant of the testaceous productions of the sea both in form and colouring; the former is rare. The recent species are not numerous, they inhabit the Indian Ocean. A fossil species occurs at Grignon, near Paris. Fig. 419, H. ventricosa.

HARPAX. Parkinson. Part of Plicatula, Auct.

HARPULA. Sw. A group of shells separated from Voluta, Auct. thus described, "shell generally tuberculated or longitudinally ribbed; apex of the spire papillary, smooth, and in general distorted; pillar with numerous distinct plaits; the upper, small and slender, the lower, thickest and shortest."—Type, H. Vexillum. (Voluta, Auct.)

HAUSTATOR. Montf. A genus proposed to include those species of Turritella, Auct. which have angulated whorls.

HAUSTELLARIA. Sw. A sub-genus of Murex, consisting of species with long canal and no spines. Murex Haustellum, fig. 396.

HAUSTRUM. Humph. Purpura, Lamarck.

HELCION. Montfort. A genus composed of species of Patella, which have the apex distinctly and prominently bent forwards. Ex. P. pellucida, fig. 230.

HELENIS. Montf. A genus of microscopic Foraminifera.

HELICELLA. Fer. One of the sub-genera into which De Ferussac has divided the genus Helix, consisting of depressed species with large umbilicus, such as Helix Algira, fig. 279. Gonites Montf.

HELICIFORM. Shaped like shells of the genus Helix.

HELICIGONA. One of De Ferussac's sub-genera of the genus Helix, consisting of angulated species, such as Carocolla Lamarckii, fig. 277.

HELICINA. Lam. Fam. Colimacea, Lam. Ellipsostomata, Bl.—Descr. Globose, compressed, or angulated, generally light and thin; aperture trigonal or semilunar; outer lip thickened and generally more or less reflected; inner lip spread over the body whorl, frequently callous near the columella, which is short, and terminates in a notch, angle, or slight callosity.—Obs. This genus of land shells, distinguished from the genus Helix, by having an operculum and a thickened columellar lip, differs also from Cyclostoma in having the aperture semicircular or angular, the peritreme discontinuous and the operculum concentric. These shells are generally small in size, and simple in form. Lamarck describes only three or four species. Mr. Gray described some others in the Zoological Journal, and in a work shortly to be published by the author, a monograph of the genus will contain descriptions and figures of at least 60 distinct species; some of which have been lately brought to this country by Mr. Cuming from the Philippine Islands. They mostly belong to tropical climates.

HELICITES. Bl. Part of the genus Nummulites, Lam. Rotalites and Egeon, Montf.

HELICOGENA. Fer. A sub-genus of Helix, consisting of species, which, like the common garden snail, fig. 268, are globose and simple in form.

HELICOLIMAX. Fer. Vitrina, Drap. H. Pellucida, fig. 263.

HELICOPHANTA. Fer. A sub-genus of Helix, consisting of ear-shaped species with large open apertures.

HELICOSTYLA. Fer. A sub-genus of Helix, consisting of species with numerous whorls, as H. Epistylium, fig. 281.

HELISOMA. Sw. A sub-genus of Planorbis. Sw. p. 337.

HELIX. Auct. Fam. Colimacea, Lam.—Descr. Orbicular, light, generally globular; spire short, last whorl ventricose, aperture oblique, peritreme reflected, interrupted by the most prominent part of the body whorl; columella confluent with the outer lip, and contiguous to the axis of the shell. No operculum; a thin epidermis.—Obs. The land shells composing this genus are found in all parts of the world; the common snail, H. Aspersa, is well known as a destructive animal in our gardens. The genera Helix, Achatina, Bulinus, Clausilia, Anostoma, &c., have been united under one generic name by De Ferussac, and again divided under the following sub-generic names, each of which we shall illustrate by a figure. Genus Helix: Sub-genus 1, Helicophanta, consisting of species with large apertures, like Vitrina; Helix brevipes. S. gen. 2, Cochlohydra, Succinea Amphibia, Drap. S. gen. 3, Helicogena, consisting of the common species with the last whorl large; Helix Hæmastoma, H. Contusa, (Streptaxis, Gray,) H. Aspersa. S. gen. 4, Helicodonta, consisting of species with teeth or folds on the columella; Polydonta, Montf. Anostoma, Helix Nux-denticulata. S. gen. 5, Helicigona, Carocolla, Geotrochus. S. gen. 6, Helicella, consisting of depressed species with a large umbilicus; H. Citrina (Naninia, Gray.) S. gen. 7, Helicostyla, consisting of species with a simple aperture, like the Helicogenæ, but with the whorls increasing very gradually; H. epistylium. S. gen. 8, Cochlostyla, Bulinus. S. gen. 9, Cochlitoma, Achatina. S. gen. 10, Cochlicopa, Polyphemus Glans. S. gen. 11, Cochlicella, Bulinus decollatus. S. gen. 12, Cochlogena, Azeca tridens. S. gen. 13, Cochlodonta, Pupa Uva. S. gen. 14, Cochlodina, Clausilia macascarensis, Balea fragilis. The last three sub-genera are included in the genus Odostomia of Fleming. We give an example of each of these sub-divisions, for the sake of presenting the reader with the principal variations to which the genus is subject. The established genera will be characterized in their places. Fig. 254 to 281.

HELIXARION. Fer. Vitrina, Drap. Differing from Helicolimax in the structure of the animal. Fig. 262.

HEMICARDIUM. Cuv. (ἡμισυς, hemisus, half, Καρδια, cardia, heart.) Cardium Hemicardium, fig. 123**, and several similar species.

HEMICYCLA. Sw. A sub-genus of Helix.

HEMICYCLONOSTA—see Cardilia.

HEMICYCLOSTOMATA. Bl. The fourth family of Asiphonibranchiata, Bl. described as "more or less globular, thick, flattened on the under side; spire very short; aperture large, semilunar, entire; its outer edge hollowed; its inner or columellar edge straight, sharp and septiform." This family answers to the genus Nerita of Linnæus, and to the family Neritacea of Lamarck. It contains the genera Natica, Nerita, Neritina, and Navicella.

HEMIMACTRA. Sw. A sub-genus of Mactra, thus described: "General form of Mactra; but the cardinal teeth entirely wanting; cartilage internal, central, in a large triangular cavity; lateral teeth 2/1, distinct, lateral, striated: connected to the Glycimeri. H. gigantea, Lam. v. 472. No. 1. grandis, Sw. Sp. Nov." Sw. p. 369.

HEMIMITRA. Sw. A sub-genus of Paludomus, Sw. (Melanianæ.)

HEMIODON. Sw. A sub-genus of Anodon, described as having "Tubercles or undulations on the hinge margin. H. undulatus, purpurascens and areolata."

HEMISINUS. Sw. A sub-genus of Melania, thus described: "General shape of Melania; but the base of the aperture is contracted and emarginate; outer lip crenated. H. lineolata, Griff. Cuv. xii. pl. 13. fig. 4."

HEMITOMA. Sw. A sub-genus of Emarginula, thus described: "Patelliform; the fissure not cut through the shell, but merely forming an internal groove. H. tricostata, Sw. Sow. Gen. fig. 6."

HEMITROCHUS. Sw. A sub-genus of Geotrochus, Sw. H. hæmastoma. Sw. p. 331.

HEPTALASMIS. Leach. (Ἡπτα, hepta, seven; ελασμα, elasma, plate) A small shell resembling Pentelasmis, from which it differs in the number of valves, being composed of seven valves according to Leach, and of eight according to Gray, who counts the dorsal valve, which is jointed, as two, and names his genus Octolasmis. Fig. 41, H. Warwickii.

HERCOLES. Montf. A microscope shell, appearing from De Montfort's figure to resemble Trochus Imperialis in shape.

HERION. Montf. Lenticulina, Bl. Microscopic.

HERMAPHRODITA. Bl. The third sub-class of Paracephalophora, Bl. divided into, Sect. 1, symmetrical, containing the orders Cirrobranchiata and Cervicobranchiata; Sect. 2, non-symmetrical, order, Scutibranchiata.

HERMES. Montf. A genus composed of Conus Nussatella, Auct. and other elongated, cylindrical, striated species. Fig. 460.

HETEROBRANCHIATA. Bl. The fourth order of the class Acephalophora, Bl. containing no testaceous mollusca.

HETEROPODA. Lam. The fifth order of the class Mollusca, Lam. This order contains but one genus of shells, viz. Carinaria, fig. 488.

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

HIATELLA. Daud. Fam. Lithophagidæ, Lam. A genus composed of species of Saxicava, Auct. which have sharp, angulated, posterior ridges, a circumstance which occurs to many species in a young state, which afterwards become rounded off. Fig. 95, Hiatella biaperta.

HIATULA. Sw. A genus proposed to include those species of Oliva, Auct. which have widened apertures. Ex. O. Subulata, fig. 458.

HIBOLITHES. Montf. A genus composed of species of Belemnites, Auct. which are swelled towards the apex, and contracted near the centre. B. Hastatus, Auct. fig. 468.

HIMANTOPODA. Schum. Malleus, Auct.

HINGE. The edge of the bivalve shells near the umbones, including the teeth and ligament.

HINNITES. Defr. A generic name proposed for Pecten Pusio, Auct. remarkable for the irregularity of the outer surface, which would almost lead to the belief of its being an attached shell. Fig. 173, H. Pusio.

HIPPAGUS. Lea. (Horse boat.) A minute fossil shell, resembling Isocardia in form, but destitute of hinge teeth. H. Isocardioides, fig. 128.

HIPPOCHRENES. Montf. Species of Rostellaria, Auct. with the outer lip spread. Fig. 403. R. Columbaria.

HIPPONYX. (Ἱππος, hippos, horse; ονυξ, onyx, nail or hoof.) Fam. Rudistes, Lam.—Descr. Inequivalve, sub-equilateral, rather irregular, destitute of ligament and hinge teeth; lower valve attached, flat, sub-orbicular, with a muscular impression, composed of two lunulate portions, meeting at one extremity, and presenting the form of a horse-shoe; upper valve conical, with the apex inclined backwards, and the muscular impression marginal.—Obs. The earlier naturalists having only met with the upper valve of these shells, placed them among the patelliform univalves; to some of which, particularly Pileopsis, they bear a very strong resemblance. The species of Hipponyx are numerous, and till lately only known in a fossil state. The recent species belong to tropical climates: the fossil species are found in the tertiary beds. Fig. 199, H. Cornucopia.

HIPPOPODIUM. Conybeare. Fam. Cardiacea, Lam.—Descr. Equivalve, obliquely transverse, heavy, deep, inequilateral, umbones incurved; ventral margin sinuated, so as to give a bilobed appearance to the shell; hinge incrassated, with one rugged oblique tooth.—Obs. These fossils are found in the upper beds of Lias. Fig. 129, H. Ponderosum.

HIPPOPUS. Lam. (Ἱππος, hippus; πους, pous, foot.) Fam. Tridacnacea, Lam.—Descr. Equivalve, inequilateral, regular, subquadrate; lunule closed, flat, with crenulated edges; ventral margin deeply undulated; external surface fluted, with radiating ribs, which are transversely fringed with rows of tubular spines; hinge margin thick, with two long, compressed posterior lateral teeth in one valve, three in the other; ligament marginal, external.—Obs. The shell thus described is rightly separated from Tridacna, on account of the anterior dorsal margins being closed; whereas in Tridacna there is a wide hiatus. Only one species of this genus is known, which receives its name from its resemblance in form to a horse's foot, when held with the flat anterior dorsal margin downwards. Few shells are found to concentrate so many beauties as the Hippopus Maculatus, commonly called the Bear's-paw-clam; the delicate whiteness of the interior, the undulating edge, the radiated fluted columns, adorned at intervals by crisped fringes, and the richness of the variegated colouring, are such as to secure the admiration of the most superficial observer. From the Indian Archipelago. Fig. 156, H. Maculatus.