The singular and beautiful transparent shell contained in this order, under the generic name Carinaria, forms a covering to a small portion of an animal, equally remarkable and equally distinct from those of all other orders.
The above arrangement, although far from perfect, and requiring numerous modifications, is perhaps liable to as few objections as any other yet proposed, and will certainly be more easily understood by those who have not the opportunity of studying the soft parts of the animal.
CONCHOLOGICAL MANUAL.
ABIDA. Leach. A genus founded on a species of Pupa, which has the peristome slightly reflected, and numerous plaits in the aperture. Pupa Juniperi, Pupa secale, Draparnaud. Great Britain; also Central and Southern Europe.
ABRA. Leach. A genus composed of Amphidesma tenue, prismaticum, and other small thin species. British Channel and Mediterranean. Fam. Mactracea.
ABSIA. Leach. Lithotrya, Sowerby. Fam. Pedunculated Cirripedes.
ACAMAS. Montfort. Belemnites multiforatus, Blainville. A species described as being perforated at the apex, by a stellated perforation. No species of Belemnite at present known agreeing with the description; it is supposed to have been taken from a broken specimen.
ACANTHOCHETES. A name given to a species of Chiton having bunches of bristles at the sides of the valves.
ACARDO. Commerçon. Described from a pair of bony plates, taken from the vertebræ of the Whale, and mistaken for a bivalve shell, destitute of a hinge.
ACARDO. Swainson. A generic term applied by Swainson to the nearly toothless species of Cardium, named C. edentulum by some authors; C. Greenlandicum by others: fig. 123*.
ACASTA. Leach. Order, Sessile Cirripedes, Lamarck. Balanus Montagui, Sowerby. A small genus separated from Balanus, on account of the cup-shaped base, but re-united by Sowerby, who shews, in his Genera of Shells, that this is a merely accidental circumstance, resulting from the situations in which the shells acquire their growth. If, for instance, the Balanus be attached to a flat surface, in an open situation, the base will be short and flat; if it be placed in a hollow among other growing substances, it will be lengthened out in order that the aperture of the shell may be even with the outer surface of the surrounding mass; and if, as in the Acastæ, it be imbedded in a soft and loose substance, the base, being left to itself, will take a regular form. The Acastæ are found imbedded in sponges. Ex. Balanus Montagui, of Great Britain, fig. 26. Also found in the Pacific ocean and Philippines.
ACAVUS. Montfort. Fam. Limacinea, Blainville; Colimacea, Lamarck. A division of the genus Helix, which may be considered synonymous with De Ferrusac's sub-genus Helicogena. De Montfort has given H. Hæmastoma, as an example. Fig. 267.
ACCESSARY VALVES, are the smaller or less important testaceous plates, found on the hinge or dorsal margins of the true valves of some shells. Example, the small plates on the hinge of Pholas, fig. 55, a. The Pholades were placed by Linnæus and Bruguière among multivalve shells.
ACEPHALOPHORA. Blainville. (a, without; κεφαλε, head.) The third class of the type Malacozoaria, Bl. including all bivalve shells, the animals of which have no distinct head. This class corresponds with the Conchifera of Lamarck, and is divided into the orders Palliobranchiata, Rudistes, Lamellibranchiata, and Heterobranchiata, the last of which contains no genera of testaceous Mollusca.
ACHATINA, Auctorum. Fam. Colimacea, Lam. (from Achates, an agate.) Fam. Limacineæ, Bl. Gen. Polyphemus, Montf.—Descr. Shell oval or oblong, sub-turrited, light, thin; aperture oval, or pyriform; outer lip sharp; columella smooth, tortuous, truncated, so as to form a notch at its union with the outer lip.—Obs. It is from this notch that we are enabled to distinguish Achatinæ from Bulini, which, moreover, generally have a reflected outer lip. The Polyphemi of Montfort have an undulation in the centre of the outer lip. Achatina Virginea, fig. 286. Polyphemus Glans, fig. 288. These land shells are found in various parts of the globe, but attain the greatest size and richness of colouring in tropical climates; particularly in the West India Islands.
ACHATINELLA. Sow. A small group of shells, differing from Achatina in having the inner edge of the outer lip thickened, and a slight groove near the suture of the spire. Fig. 287. Sandwich Islands.
ACHELOIS. Montf. Conilites Achelois. Knorr. Supp. T. 4, fig. 1.
ACICULA. Nilson. Achatina Acicula, Auct. Cionella, Jeffreys.
ACIONA. Leach. A genus described by De Blainville as consisting of those species of Scalaria, the whorls of which do not touch each other. If this account be correct, the genus proposed by Leach will include the typical species of Scalaria, such as S. pretiosa.
ACME. Hartmann. A genus formed of Turbo fuscus, Walker. Auricula lineata, Drap. thus described—"Shell sub-cylindrical, with a blunt tip; mouth ovate, simple, thin, slightly reflected over the pillar, forming a slight perforation." The animal is said to resemble a Cyclostoma, but has no operculum. Auricula lineata, Drap. Hist. 57, t. 3, fig. 20, 21. Southern Europe.
ACTEON. Montf. Tornatella, Lam.
ACTINOCAMAX. Stokes. A genus of Belemnitiform Fossils.
ACULEATED. Beset with sharp spines, as the margin of Chiton aculeatus, fig. 227.
ACUMINATED. Terminating in a point, as the apex of Melania subulata, fig. 313.
ACUS. Humphrey. Terebra of Lamarck.
ACUTE. Sharp, pointed, or sharp-edged.
ADDUCTOR MUSCLE. That which draws the two valves of a shell together, and leaves a mark on the inner surface of each, called the Muscular Impression.
ADELOSINA. D'Orb. A genus of microscopic Foraminifera.
ADESMACEA. Bl. (a, without; Δεσμα, desma, ligament.) The 10th family of the order Lamellibranchiata, Bl. composed of Mollusca which either bore tubular dwellings in rocks, wood, &c. or live in testaceous tubes, their shells being consequently destitute of the hinge ligament. The action of opening and shutting the valves being limited to the narrow space to which they are confined, or else the valves themselves being soldered into the tube, renders it unnecessary for them to have a ligament to keep them in their places. The genera Pholas, Teredina, Fistulana, and Septaria, belong to this family, which corresponds in part with the families Tubicolaria and Pholadaria, of Lamarck.
ADNA. Leach. One of the genera separated by Leach from Pyrgoma, and characterized as consisting of an upper valve, supported on a funnel-shaped base, which is not buried in the coral to which it is attached, like Pyrgoma, but is seen externally. The operculum consists of four valves. Adna, fig. 32. British Channel and Mediterranean.
ADNATE. A term applied by some authors to those shells belonging to the family of Unionidæ, which have the valves joined together at the dorsal margin, not like other bivalves, by a distinct ligament, but by the substance of the shell itself, the valves appearing to grow together in such a manner that they cannot be separated without one of them being broken as will be seen in our figure of Dipsas plicatus, fig. 142. This circumstance has been made the foundation of specific and even generic distinctions, for which however it is insufficient, because many species which when young are "adnate," when fully grown have their valves joined together only by a ligament.
ÆGLIA. Say. A division of "Unionidæ," described as having the "shell cuneate; bosses prominent; cardinal teeth much compressed, placed on one side of the bosses. Æglia ovata, Say. Occidens Lea. Am. Tr. iii. pl. 10." Lardner's Encyclopedia of Malacology.
AGANIDES. Montf. Orbulites, Lam.
AGATHIRSES. Montf. Siliquaria, Auct.
AGINA ——? Belongs to Saxicava, Auct.
AKERA. Bl. The fourth family of the order Monopleurobranchiata, Bl. containing the genera Bulla, Bullæa and Bellerophon, which, excepting the last, constitutes the family Bullæana, Lam.
AKERA. A genus of extremely light, horny shells, resembling Bulla, from which it differs, in the outer lip being separated from the body whorl, which is elastic. Ex. Bulla fragilis, fig. 247.
ALÆA. Jeffrey's. A genus of minute land shells, resembling Vertigo, but separated because they are dextral, while Vertigo is sinistral. Ex. fig. 292. A. marginata, Pupa marginata, Drap. found in marshy ground, roots of trees, moss, &c. Britain and Southern and Central Europe.
ALASMODON. Say. A division of the genus Unio, Auct. consisting of those species which have cardinal, but no lateral teeth. Ex. A. complanatus, fig. 141. North America and Europe.
ALATÆ. Lam. A family of the order Trachelipoda, Lam. containing the following genera which may be thus distinguished.
1. Rostellaria. Sinus close to the canal; including Hippochrenes, and Aporrhais, Fig. 402 to 404.
2. Strombus. Sinus not close to the canal. Fig. 406.
3. Pteroceras. Same, digitated. Fig. 405.
ALATED. (From Ala, a wing.) Winged, a term applied to shells, when any portion of them is spread out in any direction, as in fig. 403. Hippochrenes, Montf. and fig. 147, Unio Alatus.
ALCADIA. Gray? (B. M. Syn. p. 134) Helicinæ which have a notch in the aperture. A distinction which it is impossible to maintain. See Helicina.
ALATUS. Humphrey. Strombus, Auct.
ALECTRION. Montf. Buccinum Papillosum, Auct. fig. 422.
ALEPAS. Rang. A genus of Pedunculated Cirripedes without a shell.
ALVEOLINA. D'Orbigny. A genus of microscopic Foraminifera.
AMALTHUS. Montf. A. margaritaceus, Montf. is a species of Ammonites described as very flat, keeled, with an angular aperture. It belongs to the family Ammonacea, Lam.
AMARULA ——? A genus composed of Melania Amarula, Auct. and similar species.
AMBIGUÆ. Lam. The fourth section of the order Conchifera Dimyaria, containing the family Chamacea, fig. 153 to 155.
AMICULA. A genus formed for the reception of Chiton amiculatus, Auct. the valves of which are covered by an integument; so as to be completely hidden externally.
AMIMONUS. Montf. Conilites ungulatus, Knorr. A species distinguished only by being slightly curved; Fam. Orthocerata, Lam.
AMMONACEA. Bl. The fourth family of the order Polythalamia, Bl. or chambered shells, described as thin, chambered, discoidal, convolute, symmetrical, generally compressed, with visible whorls. This last character is used in De Blainville's System to distinguish the Ammonacea from the Nautilacea. This family contains the genera Discorbites, Scaphites, Ammonites, and Simplegas.
AMMONACEA. Lam. The seventh family of Polythalamous Cephalopoda, Lam. containing the genera Ammonites, Orbulites, Ammonoceras, Turrilites and Baculites, to which may be added Amalthus, Simplegas, Ellipsolites, Nautellipsites, Hamites, Icthyosarcolites, and other genera mentioned in the list of figures 477 to 484.
AMMONITES. Auct. (from Jupiter Ammon.) Fam. Ammonacea, Lam. and Bl.—Descr. Symmetrical, convolute, discoidal, orbicular; chambers numerous, divided by lobated, branched or sinuous septa, perforated by a Siphon; aperture generally more or less modified by the last whorl. The fossils of the secondary strata which compose this genus are numerous and well known; they are vulgarly termed "snake-stones," and some of them are extremely beautiful, particularly when the internal structure is exhibited by a section. There is some difficulty in distinguishing them from the Fossil Nautili, for although the whorls, being visible and the Septa sinuous, may be taken as the characteristics of the Ammonites, yet there are several species which partake the characters of both. The Orbulites of Lamarck (fig. 479) for instance, have sinuous septa like Ammonites, but the last whorl covers those which precede it as in Nautilus. Simplegas Montf. and Bl. (fig. 475) has the whorls visible externally and the septa simple. Ammonites is figured in the plates (478).
AMMONOCERAS, or AMMONOCERATITES. Lam. (from Ammon & Κερας, ceras, horn.) The shells described under this Lamarckian genus present an anomaly which is considered by Mr. G. B. Sowerby, sen., as merely accidental. They resemble the Ammonites in internal structure, but instead of being spirally convolute they are merely curved like a horn. Ex. fig. 477, copied from De Blainville.
AMNICOLA. The name of a genus mentioned in the family of Melaniana in the conchological part of the Synopsis of the British Museum, but unexplained.
AMPHIBOLA ——? The same as Ampullaria, Auct.
AMPHIBULIMA. Lam. Succinea Patula, Auct. (fig. 266.) was first published in the Ann. du. Mus. D'Hist. Nat. under the name Amphibulima cucullata. The generic name was afterwards abandoned by its author, and the species stands in his system as Succinea cucullata. West Indies.
AMPHIDESMA. Lam. (from Αμφω, ampho, ambo, Δεσμος, desmos, ligamentum). Fam. Mactracea, Lam.—Descr. Equivalve, oval or rounded, sub-equilateral, sometimes rather gaping at the sides, with slight posterior fold; hinge with one or two cardinal teeth in each valve, and two elongated lateral teeth, distinct in one valve, nearly obsolete in the other; ligament short, separated from the cartilage, which is elongated and couched obliquely in an excavation of the hinge.—Obs. In most bivalve shells, the cartilage and ligament are united in one mass, or placed close to each other; the contrary in this case gives rise to the name, which signifies double ligament. This circumstance distinguishes the genus Amphidesma from Tellina, which in other respects it greatly resembles. From Lutraria it may be known by its distinct lateral teeth, and also by its valves being nearly close all round, while the Lutrariæ gape anteriorly. The species do not appear to be numerous, no fossil species are known. A. Reticulatum, fig. 85. West India Islands, Brazil, Coast of Pacific, &c.
AMPHIPEPLEA. Nilson. The type of this proposed genus is Limnea glutinosa, Auct. Gray's edition of Turton, page 243, plate 9. fig. 103. The shell is polished and the inner lip expanded.
AMPHISTEGINA. D'Orb. A genus of microscopic Foraminifera.
AMPLEXUS. J. Sowerby. A. Corralloides, fig. 463. A singularly formed fossil, described as nearly cylindrical, divided into chambers by numerous transverse septa, which embrace each other with reflected margins. It occurs in the Dublin limestone, and resembles a coral or madrepore.
AMPLEXUS. A generic name proposed by Captain Brown for Helix pulchella, Drap. 112, tab. 107-134. Zurama, Leach.
AMPULLARIA. Auct. (Ampulla, a rounded vessel). Fam. "Peristomiens," Lam. Ellipsostomata, Bl.—Descr. Spiral, globular, sometimes discoidal, frequently umbilicated, covered with a rounded, horny epidermis; spire short; whorls rapidly enlarging; aperture elliptical, rounded anteriorly; peristome nearly or quite entire, thickened and slightly reflected; operculum, testaceous, annular, with a subcentral nucleus.—Obs. This genus of fresh-water shells of which a few fossil species occur, is easily distinguished from other genera, by obvious characters, particularly by a thick, horny, greenish-brown epidermis, and the rotundity in form. One species, the A. Cornu-arietis which forms the type of Lamarck's genus Planorbis, requires notice on account of its flatness, but may be known by the aperture which in the Ampullaria is longer than wide, and in Planorbis the contrary. Lanistes, Montf. is described from a reversed species of Ampullaria. The Ampullaria is vulgarly called the Idol Shell, and is said to be held in great veneration by the South American Savages. The animal has a large bag, opening beneath, placed on the side of the respiratory cavity. It is supposed that the animal has the power of filling this bag with water, and that it is thus enabled to live a long time out of water. They have been brought as far as from Egypt to Paris alive, packed in saw-dust. Ex. fig. 318. East and West Indies, North Africa, South America, &c.
AMPULLARINA ——? A genus formed for the reception of Ampullaria avellana. Fig. 538. From Australia.
AMPULLINA ——? Part of the genus Helicina, Auct.
ANALOGOUS. A term applied to certain species of fossil shells, which present a certain degree of resemblance to recent species; but which are not sufficiently similar to warrant the use of the term 'identical,' or any other implying that they are of the same species.
ANASTOMA or ANOSTOMA. Fischer. (from Ανα, ana, backwards; Στομα, stoma, mouth) Fam. Colimacea, Lamark. A genus of land shells so named from the singular circumstance of the last whorl taking a sudden turn and reflecting the aperture upwards, so as to present it on the same plane with the spire; so that the animal walks with the spire of the shell downwards resting on the foot. In other respects, the two species of which this genus is composed, resemble other Helices; and belong to De Ferrusac's division "Helicodonta." Tomogerus is De Montfort's name for this genus. A. depressum is represented in the plates figs. 271, 272. The nearest approach to this genus will be found in the fossil shell named Strophostoma, by Deshayes, which, however, has no teeth in the aperture and is provided with an operculum like Cyclostoma. South America.
ANATIFER. Brug. Anatifa, Lam. This name, which signifies Duckbearing, has been given to the shells commonly called Barnacles, on account of an absurd notion entertained among the ancients, that they inclose the young of the Barnacle duck, in an embryo state. The beautiful bunch of jointed arms, the ciliæ of which serve the purpose of agitating the water, so as to draw in food by the current, were supposed to be the feathers of the future bird. For a description of these shells, see Pentelasmis; and fig. 34.
ANATINA. Lam. (That which belongs to a duck.) Fam. Myaria, Lam. Pyloridea, Bl.—Descr. Thin, transparent, generally equivalve, inequilateral, transverse, marine; hinge with a spoon-shaped process in each valve, containing the cartilage.—Obs. Some species included in the genus Anatina of authors, A. striata, for instance, have not the spoon-shaped prominence, but in its place a small, testaceous, moving appendage, connected with the interior of the hinge. These are now separated, and form the genus Lyonsia. The genus Næara, Gray, is composed of Anatina longirostrum, and similar species, which have neither the bony appendage nor the spoon-shaped prominence. Mya is distinguished from Anatina, by the thickness of the shell, and also by having the prominence only in the hinge of one valve. Fig. 69. A. rostrata. The Anatinæ are found in the East Indies and South Sea Islands.
ANATINELLA. G. B. Sowerby. (Dimunition of Anatina). A genus so named from its resemblance to Anatina, from which it differs in being destitute of the internal appendage, and having no sinus in the palleal impression. One species having been brought from Ceylon, received the name of Anatinella Sibbaldii. Another has lately been found in the Philippine Islands. Fig. 70.
ANATOMUS. Montf. Tom. 2, plate 279. A microscopic shell, appearing from the figure to resemble Scissurella.
ANAULAX. Brogn. Ancillaria, Auct.
ANCILLA. Lam. Ancillaria, Auct.
ANCILLARIA. Auct. Ancilla, Lam. (A handmaid.) Fam. convolutæ, Lam. Angyostomata, Bl.—Descr. Smooth, oblong, subcylindrical. Spire short, sutures hidden by enamel. Aperture long, anteriorly emarginated and somewhat effuse. Columella tortuous, oblique, tumid, truncated.—Obs. The Ancillariæ are pretty shining shells, enveloped almost entirely by the soft parts of the animal. They resemble Oliva, from which they are distinguished by the suture of the spire being filled up with shelly enamel, nearly covering the surface. The whorls in Oliva being separated by a distinct canal. Ancillaria may be known from Terebellum by the tumid varix at the base of the columella. The well known Ivory shell, Eburna glabrata, Lam. belongs to this genus, of which a few fossil species are found in the London clay, Calcaire grossièr and green sand, Turin. The recent species are found in the Islands of the Indian Ocean and Australian Seas. A. glabrata is represented in the plates fig. 455; A. cinnamonea, fig. 456.
ANCULOSA. Say. Fam. Melaniana, Lam. Ellipsostomata, Bl. A genus proposed to include some fresh-water shells resembling those of the genus Melania, the difference between them being that the spire of Anculosa is more depressed, and the anterior of the outer lip more angulated than in Melania. On an examination of the different species, however, it will be found that this is quite unsatisfactory, as a generic distinction; because some of the species with short flattened spires, have rounded, and others angulated apertures. North America. An example of each is represented, fig. 314.
ANCYLUS. Geoffroy. Fam. Calyptracea, Lam. Otides, Bl.—Descr. Thin, obliquely conical, patelliform; apex acute, turned sidewise and backwards; aperture oval; margin simple.—Obs. Although the little fresh-water shells described under this name, resemble those of the genus Patella, the animals which produce them are nearly allied to the Lymneanæ. And, it may also be observed, that the shells themselves differ from Patella in not being quite symmetrical, having the apex turned on one side. A. fluviatilis, fig. 246. Found in Great Britain, and in Southern and Central Europe, West Indies, &c.
ANDROMEDES. Montf. Vorticialis, Lam. Fam. Nautilacea, Lam. A genus of microscopic Foraminifera.
ANGULATED. (Angulatus.) Having an angle, or corner, as the anterior of the aperture of Eulima, fig. 348; the posterior side of Castalia, fig. 140; the whorls of Carocolla, fig. 277.
ANGULITES. Montf. A genus composed of species of fossil Nautili, described by De Blainville as not umbilicated, with a dorsal keel and angular aperture. Nautilus triangularis Buffon.
ANGIOSTOMATA. Bl. The third family of Siphonobranchiata, Bl. described as differing little from the family of Entomostomata, but having long, narrow, straight apertures, and the columellar lips straight or nearly so. Were it not for the admission of the genus Strombus into this family, it would correspond with Columellaria and Convolutæ of Lamarck.
ANNELIDES. The ninth class of invertebrated animals, divided into three orders, namely, A. Apodes, A. Antennés, and A. Sedentaires. The last only contains families of testaceous Mollusca. The animals are vermicular, some naked, others inhabiting shelly tubes. See Sedentary Annelides.
ANNULAR OPERCULUM is one which has the nucleus central, or nearly so, the other layers surrounding it in flattened rings. The term concentric is also applied. See Introduction.
ANNULATED. (Annus, a ring.) Composed of, or surrounded by rings, as in the case of Tubicinella, fig. 14.
ANODON. Brug. Fam. Submytilacea, Bl. Nayades, Lam. A genus composed of such species of Nayades as are destitute of teeth on the hinge. Europe, North America, &c. An example is given in A. Cataractus, fig. 152.
ANOMALINA. D'Orb. A genus of microscopic Foraminifera.
ANOMIA. Fam. Ostracea, Lam. and Bl.—Descr. Irregular, inequivalve, sub-equilateral, foliaceous, pearly within; adhering to marine substances by means of a bony appendage, which passes through a large circular opening in the lower valve; muscular impression divided into three irregular portions; hinge destitute of teeth with a short cartilage.—Obs. The Linnæan genus included not only the shells to which the description above given would apply, but also many other genera, such as Crania, Orbicula, Terebratula, &c. which belong to the Brachiopoda, and are perfectly distinct. The Anomiæ are found in Europe, N. America, Moluccas, Philippine Islands, &c. Fig. 186, in the plates, is a somewhat reduced representation of a full grown specimen of A. Ephippium. Fig. 187, the hinge of the under valve, with the bony process. Fig. 188, the hinge showing the opening through which it passes.
ANOSTOMA. See Anastoma.
ANSATES. Klein. A genus formed of those species of Patella which have a produced, recurved beak. Helcion, Montf. Ex. Patella pellucida, fig. 230.
ANSULUS or ANSYLUS. Mr. Gray conjectures that the name of the genus Ancylus, should be so written.
ANTENOR. Montf. A genus of microscopic Foraminifera.
ANTERIOR. In Bivalves is the side on which the head, or part analogous to the head of the animal lies; it is known in the shell by the umbones, which if turned at all, are turned towards that part. If there be a sinus in the impression of the mantle, it is always on the posterior part of the shell. If the ligament be placed only on one side of the umbones, it is only on the posterior side. The anterior of a spiral univalve is that part of the outer lip which is at the greatest distance from the apex. Of a symmetrical conical univalve such as Patella, it is that part where the head of the animal lies, indicated by the interruption of the muscular impression. Of cirripedes, that part where the ciliæ protrude are anterior; of Brachiopoda, that part which is farthest from the umbones and which corresponds with the ventral margin in other Bivalves. The anterior of symmetrical, convolute univalves, is the outer or dorsal part of the aperture, or that part which is farthest from the spire. Lamarck and other Conchological writers have occasioned much confusion by their errors on this subject; describing the same part of a shell at one time anterior, at another posterior; but generally the reverse of the above arrangement, which is founded upon the natural position of the animal, and generally adopted. The anterior will be indicated by the letter a, in figs. 119, 421, 229, 34, 202.
ANTIGONA. Schum. A genus composed of Venus cancellata, Lam. (fig. 119.) and similar species.
ANTIQUATED. This word, signifying out of date, is occasionally used to express that species of composition which constantly occurs in shells, by each fresh deposit or layer of calcareous matter, forming a new margin, which being replaced by its successor, is no longer used as the margin, and is consequently said to be out of date.
APEX. This term does not apply to the natural position of a shell, but is used in a mathematical sense, to indicate the nucleus or first formed part; which may be considered as the point of the spiral cone. From this point, the shell enlarging rapidly or slowly as it descends, takes a spiral, arched, straight, oblique, convolute, or irregularly spiral course. The apex will be indicated by the letter a, in fig. 282 and 466.
APERTURE or MOUTH. The entrance to the spiral cavity of univalve shells. The parts of the aperture are separately described, as follows: The inner lip or labium is that part which lies over the preceding whorl of the shell. It terminates anteriorly, or towards the lower part in what is termed the columella, so called because it forms a kind of axis on which the volutions turn. The outer lip, sometimes called the labrum, is on the opposite side, or the farthest from the axis. If the edges of the inner and outer lips unite all round, they are described as composing the peritrême. In fig. 318, the aperture is marked by the letter a.
APHRODITA. Lea. (from Αφροδιτη, Greek name of Venus.) A genus composed of Cardium Groenlandicum, Auct. fig. 123*, and other similar species of Cardium, the teeth of which are either wholly wanting, or very indistinct. Northern Ocean.
APICIAL. Belonging to the apex. The apicial extremity of the aperture of a univalve shell, is that which is nearest to the apex of the spire.
APICULUM. Humph. Trochus, Lam.
APLEUROTIS. Rafinesque. A genus unfigured and imperfectly described as differing in some respects from Terebratula and other Brachiopodæ.
APLEXUS. Fleming. A genus composed of Physa Hypnorum, Drap. &c. and described as having the inner lip simple, and not spread over the body whorl.
APLODON. Rafinesque. A genus proposed to be established at the expense of the genus Helix, but upon what grounds does not appear from the imperfect description which is unaccompanied by a figure.
APLUSTRE. Schum. A genus formed for the reception of those species of Bulla which have the spire uncovered. Ex. Bulla Aplustre, (aplustre, a flag.) Auct. fig. 289.
APLYSIA. Linn. (a, without; Πλυω, to wash.) Fam. Laplysiens, Lam. Aplysiana, Bl.—Descr. Horny, transparent, clypeiform, or shield-shaped, placed horizontally on the back of the animal, with its convex side uppermost; apex slightly incurved.—Obs. The animal producing this shell has derived its name from the purplish liquor which it exudes, when disturbed. In contour, it has been fancied to present a certain likeness to a hare crouching, and on this account was called Lepus marinus, or sea hare, by the ancients. The shell bears a strong resemblance to Dolabella, which, however, is much thicker, and more testaceous. The species are found in the Mediterranean, European, and West Indian Seas. A. Petersoni, fig. 254.
APLYSIACEA. Bl. The second family of the order Monopleurobranchiata, Bl. The animals composing this family are either destitute of shells, or are provided with internal ones, which are flat, open, oblique, with the apex or nucleus slightly incurved, not distinctly spiral. This family contains the genera, Aplysia and Dolabella. The first sub-spiral, with the apex terminal; shell thin, horny. Fig. 254. The second the same, but thick and shelly. Fig. 255.
APOLLON. Montf. Ranella Ranina, Auct. Placed by De Blainville in that division of Ranella, which is characterized as being umbilicated. Fig. 393.
APOROBRANCHIATA. Bl. The first order of the second section of Paracephalophora Monoica, Bl. The Thecosmata is the only family of this order containing any approach to shells, these are Hyalæa and Cymbulia.
APORRHAIS. Petiver. A genus formed of Rostellaria Pes-pelicani, Auct. (fig. 404) and similar species. Although the shell presents no characters to distinguish it generically from Rostellaria, those who have examined the soft parts are convinced that it is distinct. Of the three species now known and figured in part I. of Thesaurus Conchyliorum, by the Author, one is common on our own coast, and in the Mediterranean; also North America. See Rostellaria.
AQUATIC. A term applied by some authors to those species of Molluscous animals, which inhabit fresh water, either in rivers, or salt water standing pools, as distinguished from the marine or Mollusca. See Fresh-water.
AQUILLUS. Montf. Triton Lampas, Cutaceus, &c. Auct. Placed by De Blainville in the division of the genus Triton, which is described as having a short spire, being covered with tubercles and umbilicated. Triton Cutaceus, fig. 399.
ARCA. Auct. (Anglicè, a boat.) Fam. Arcacea, Lam.—Descr. Obliquely transverse, subquadrate, equivalve, or nearly so, inequilateral, thick, ventricose, longitudinally ribbed, dentated near the inner margins; hinge rectilinear, forming a flat, external area, upon which the ligament is spread in cross rows, and having a series of small, regular teeth, extending on both sides of the umbones in each valve; muscular impressions distant.—Obs. The shells composing this genus are easily distinguished from those of all other bivalve shells, by the straight, linear row of small, notched teeth, and by the area between the umbones. The genus Cucullæa makes the nearest approach to it in this respect, but it may easily be known from it by the outermost teeth on each side of the row being oblique, and lengthened out; and also by the prominent edge of the muscular impression. These shells are found recent, in various marine localities; fossil, in the tertiary deposits. The Arca Noæ, formerly regarded as the type of this genus, has, with several other species, been separated from it under the name of Bysso-arca, by Swainson, on account of an hiatus in the ventral margin, to admit the passage of a byssus; this is not found in the true Arcæ. The true Arcæ are mostly tropical. Arca Antiquata, fig. 131. Bysso-arca Noæ, 132.
ARCACEA. Lam. A family of the order Conchifera Dimyaria, characterized by a series of teeth placed on the hinge in a line. The genera may be distinguished as follows,
1. Arca. Hinge straight; valves close. Fig. 131.
2. Bysso-arca. Valves gaping. Fig. 132.
3. Cucullæa. Distant teeth oblique; posterior muscular impression prominent. Fig. 133.
4. Pectunculus. Hinge curved. Fig. 134.
5. Nucula. The same, with a pit in the centre of the hinge, including Myopara and Crenella. Figs. 135 to 137.
6. Solenella. Fresh water, oval; a series of teeth on one side of the hinge, only two or three on the other. Fig. 138.
ARCHAIAS. Montf. A genus of microscopic Foraminifera.
ARCHONTE. Montf. Hyalæa, Auct.
ARCINELLA. Schum. Chama Arcinella, Auct.
ARCTICA. Schum. Cyprina Icelandica, Auct.
ARCUATED. (Arcus, an arch.) Bent in the form of an arch, as Dentalium, fig. 2.
AREA. A flat space or disc, on any part of a shell. As for instance, the triangular space on the hinge of Arca, fig. 132, and Spondylus.
ARENACEOUS. (Arena, sand.) Of a sandy texture, as the sand tubes surrounding the bodies of some of the Annellides, named Arenaria on this account. But the word is more commonly used to intimate the habits of the animal, burrowing with its shell in the sand.
ARETHUSA. Montf. A genus of microscopic Foraminifera.
ARGONAUTA. Auct. Commonly called the "Paper Sailor." Fam. Pteropoda, Bl. Order Cephalopoda Monothalamia, Lam.—Descr. Light, thin, transparent or nearly so, symmetrically convolute, carinated by a double row of tubercles, terminating smooth or tuberculated ribs radiating towards the centre; aperture large, elongated; peritrême acute, interrupted by the body whorl.—Obs. The exquisitely beautiful, light and delicate fabrics included under the above name are inhabited by a molluscous animal named the Ocythöe, which is provided with tuberculated arms. These, hanging over the sides of the aperture, give to the whole the appearance of a vessel propelled by oars: a poetical illusion further heightened by the broad, flat membranes of the two arms, which, when vertically expanded, present an idea of sails. Pliny has described the Nautilus (the name has been changed by the moderns) as sailing gracefully on the Mediterranean waters; and Pope has versified the idea in the well known lines
"Learn of the little Nautilus to sail, Spread the thin oar and catch the driving gale."