G. B. Sowerby

“ Considering the bivalve shell as a whole, it will be necessary, in the first instance, to describe the position in which it is to be observed, in order to give the student a clearly defined notion of what is intended, when terms expressive of height, depth, length, breadth, &c. are used, as well as when the anterior and posterior extremities are spoken of. For this purpose, we must suppose the animal to be living and creeping along the bed of the sea by means of its foot; where this foot protrudes, will be the ventral margin, and the opposite part the dorsal margin of the shell. ”

“ Shells of Arcadæ, 1-14, have the hinge characterized by a series of teeth on each side of the apex. Nucula, Arca, and Pectunculus are easily distinguished. Limopsis, 14, has a spring pit between the two rows. Our figure of Pinna, 16, is from a young specimen: it grows to great size, and spins a very silky byssus. The shell of Anomia, 18, is fixed to rocks, etc., by means of a bony button passing through a hole or sinus in the lower valve. Lima, 22-24, has a light, thin shell, and its mantle is adorned with beautiful fringes. ”

“ 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. ”

“ BASE. In all shells which are attached to sub-marine substances, the base is that part of the shell which forms the point of attachment,—as for instance, the attached valve of Spondylus, the basal plate of Balanus, the lower part of the peduncle of Pentelasmis; in Unattached Bivalves, the margin opposite to the umbones, where the foot of the animal, or the part analogous to it, protrudes; in spiral univalves, the aperture, which rests on the back of the animal when walking. ”

“ MUSCULAR IMPRESSIONS are the marks or areas formed on the interior surface of shells by the muscular fibres which attach the animals to them. Lamarck has divided his Conchifera into two kinds: 1st. Monomyaria, those which have but one adductor muscle, and consequently have but one impression in each valve, as the common Oyster, fig. 180; 2nd. The Dimyaria, those which have two, and consequently have two impressions in each valve. There are other smaller impressions in some shells besides the principal. The palleal impression is a mark or scar passing near the margin of the shell. ”

“ The shelly or membranaceous plate with which some of the animals enclose the aperture of their shells, during the wintry part of the year, for the purpose of protecting them while in a torpid state, and which they get rid of by dissolving the edges, when preparing to emerge from their temporary retirement, must not be considered as the operculum, as it does not belong to or form part of either the animal or its shell, but is produced for the occasion by a secretion of the animal, being deposited in a soft state and subsequently hardening. ”

“ Symmetrical Convolute Univalves.
The Nautilus, the Spirula, the Scaphite, and the Ammonite are the leading types of this form; but when we use the term symmetrical, in reference to these, the word must not be understood in its strictest sense, for no shell is perfectly symmetrical: but it means that there is no perceptible difference in the proportion of the two sides; as in the human body, the right side is larger and more powerful than the left, yet to a degree so small that it gives no apparent bias to the figure. ”

“ SCALARIA. Auct. Fam. Scalariana, Lam. Cricostomata, Bl.—Descr. Turrited, oval or oblong; spire long, composed of rounded, sometimes separate whorls, surrounded by regular concentric ribs; aperture oval, peristome reflected continuous, entire.—Obs. The typical species of this genus, commonly called the Wentletrap, (S. pretiosa) is celebrated for the beautiful appearance caused by the numerous ribs encircling the whorls, and formerly produced an immense price in the market. ”

“ Scientific men have long been engaged in the interesting discussion, whether the animal really belongs to the shell in which it is found, or whether, having destroyed the rightful owner, it has possessed itself of the "frail bark." It is now, however, proved beyond the shadow of a doubt that the Argonaut is the testaceous part of the Ocythöe, and that the broad membranes which in some representations have been artificially placed as sails, are naturally bent backwards over the shell like the mantle of some other molluscs. ”

“ 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. ”

“ Fossil species occur in the London clay, &c.
AXINUS. J. Sowerby.—Descr. Equivalve, transverse; posterior side very short, rounded, with a long ligament, placed in a furrow, extending along the whole edge; anterior side produced, angulated, truncated, with a flattish lunule near the beaks. The late Mr. James Sowerby, who described this shell in the Mineral Conchology, did not consider his genus as established, not having seen the hinge.
AXIS. The imaginary line, round which the whorls of a spiral shell revolve. The extremities of the axis are pointed out in fig. 379, by the letters, a. a. ”

“ It is accurate in its science, graceful in its style, and familiar in its language; it enables the student to take some common, or easily accessible plant, as the representative of each natural family, to examine its several parts, to compare them with the plates, and learn their uses from the descriptions; when he has done this with care, and understood, and remembered what he has done, he will be a Botanist; if not a learned one, at least acquainted with all the fundamental facts of the science. ”

“ INTERNAL SHELL is one which is enclosed in the soft parts of the animal, as a bone is enclosed in the flesh of a human body. The Limax, or common garden slug, which has a testaceous shield beneath its mantle, is an instance of this.
IO. Lea. A genus composed of several species of fresh-water shells which are considered as differing from Melaniæ in having the anterior termination of the aperture produced into a point in some degree resembling the caudal canals of shells belonging to the family of Canalifera, which are marine. ”

“ 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. ”

“ 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. ”

“ These are conical, irregular, spiral, or convolute. The conical form is when there is no enrolment of the apex. Although the Patellæ were described as symmetrical, there are several species of Patelliform shells which are not symmetrical. In Umbrella, for instance, the apex is oblique, the shells being placed obliquely on the animal. In the genus Siphonaria, there is a groove on one side, where the brachia or gills of the animal rest. In the genus Ancylus, it will be observed that the apex bends on one side, and the animal is like the Limnæa, which has a spiral shell. ”

“ When thickened and turned backwards it is described as reflected; when, on the other hand, it is turned inwards towards the axis, as in the Cyprædæ, it is inflected, or involute. When it is toothed, a distinction must be observed as to whether the dentations are external or internal. If the teeth are small and numerous, it is denticulated; if larger, it is dentated; when expanded into a kind of wing, as in some species of Strombus and Rostellaria, it is described as alated; and a family in Lamarck's system is named "Alatæ," from this very circumstance. ”

“ A genus proposed for the admission of a singular fossil shell, found on the beach at Felix-stone, of which the following are the characters;—fusiform, aperture equalling the spire in length, terminating anteriorly in a slightly recurved canal; columellar lip smooth, curved, thickened posteriorly into a blunt tooth; spire obtuse.—Obs. This shell would be a Fusus were it not for the tooth on the posterior extremity of the columellar lip. The only species known is regularly striated in a spiral direction, and named A. Elegans. ”

“ Cardia are frequent in all climates.
CARINARIA. Auct. Class, Cephalopoda. Division, Monothalamia, Lam. Fam. Nectopoda, Bl.—Descr. Symmetrical or nearly so, conical, thin, glassy, fragile, patelliform; with a fimbriated dorsal keel; apex convolute, bent forwards; aperture oval, pointed at the dorsal extremity. Hab. Amboyna, Indian Ocean, and Mediterranean Sea.—Obs. A most singular and beautiful shell, remarkable for its transparency, its fragile structure, and the dorsal keel, whence it derives its name. It was once so rare that a single specimen was known to realize one hundred guineas. Fig. ”

“ Murex may be distinguished from Triton by the continuity of the varices, which follow each other in a tortuous direction on the spire. The Ranellæ have only two rows of varices, and have a posterior as well as anterior canal; while Murices have three or more varices, and only one canal. The genus Typhis consists of several small species resembling Murex in every respect, excepting that of having a tubular opening on the upper part of the whorl between each varix. See Typhis. The most beautiful Murices are brought from tropical climates. Fig. ”

“ 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.) ”

“ In the Ranellæ, the varices run in two rows along the spire; in the Murices, they form three or more rows; but in the Tritons, they do not follow each other, i.e. they do not occur in the same part of each volution. The large species of Triton, are sometimes used as trumpets. The Tritons are brought from the Mediterranean, Ceylon, the East and West Indies, and South Seas. Fig. 398 to 401.
TRITONIDEA. Sw. A genus of "Buccininæ," Sw. thus described: "Shell bucciniform, but the basal half is narrowed, and the middle more or less ventricose; spire and aperture equal. ”

“ Those which are symmetrically convolute, as the Nautilacea and the Ammonacea, which are spiral; 2nd. Those which are not spiral, but simply conical, as the patelliform shells. Bivalves belonging to the Brachiopoda are also symmetrical. Ex. Patella, fig. 229. Ammonites, fig. 478.
SYMPHYNOTA. Lea. A genus of Nayades, in which Mr. Lea proposed to include species of the genus Unio, the valves of which are connate, or united at the dorsal margin. We believe that this distinction, as a genus, has been abandoned by its author. The fact is, that all the Uniones are Symphynotæ when in a young state. ”

“ 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. ”

“ Some species are smooth, although the greater number are imbricated or crisped outside. P. saccata, fig. 162.
PINNATED. (From Pinna, a fin.) When a part of a shell is spread out and smooth, as in Rostellaria columbaria, fig. 403, it is said to be alated, or winged, but when the part which is spread is radiated or ribbed, like the fin of a fish, it is pinnated, as in Murex pinnatus, and Murex tripterus. (Conch. Illustr.)
PIRENA. Lam. A genus of fresh-water shells, rejected by De Ferussac and other authors, who place Lamarck's two first species with Melanopsis, and his two last with Melania. ”

“ 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. ”

“ Equivalve, inequilateral, foliaceous, trilobate, undulated, irregular, attached by a byssus passing through a sinus in one valve; hinge rectilinear, lengthened by two auricles; with a small disc under the umbones, containing the ligament, and a groove containing the cartilage; muscular impressions one in each valve, large, uniform, and one or two others extremely minute.—Obs. Malleus Vulgaris, the type of this genus, is a most singular shell, commonly called the "Hammer Oyster," from the peculiarity of its shape. ”