The Conchologist’s First Book — Edgar A. Poe, 1839 — reading text

fig. 1. CC. Incurved Teeth are those which are bent round, as in the sin- gle tooth of the Solen. Plate IV. fig. 8. ff Recurved Teeth, are those which are bent backwards, as in the hinge of the Panopea. Plate XVIII. fig. 9; and Spondylus, Plate Il. fig. 8. ff Middle Teeth, Plate IV. fig. 4.d d. These are also termed Cardinal Teeth. Numerous Teeth, are those small upright teeth, set in rows, of which the hinges of all the species of the genus Arca are formed. Plate IV. fig. 10. k k. Cavity of the Hinge. The hollow depression in which the ligament of the Ostrea is situated, generally of a triangular form. Plate IV. fig. 11. &. Ligament of the Hinge, or cartilage, is that flexible fibrous sub- stance by which the valves are united, and the hinges kept in their proper places; generally situated under the beaks of the shell. Plate II. fig. 1, 3, and 4.277; Plate IV. fig. 3. 2. Beak is the extreme point of the summit of bivalves, which in many species turns spirally downwards, or to the one side, as in EXPLANATION OF THE PARTS OF SHELLS. 13 some species of Venus, &c. From this circumstance it is seldom - the highest part of the shell. Plate II. fig. 5. » r. Seam. When the valves are closed, the line of separation . _ between them is so called. Plate II. fig. 6. ¢ ¢. Umbo. That part situated immediately under the beak. Plate I.. fig. 6. w; and Plate Il. fig. 4. w. Ears, The processes on each side of the beak, in most species of that division of Ostrea, called pecten; some have one ear very large, and the other small; and some are scarcely observable on one side. Plate IV. fig. 2. A h. Superior Ear. Plate IV. fig. 11. A. Inferior Ear. Do. do. 2 /Margin. The extreme edge of the whole shell, or the circum- ference of either valve, all round. Plate I. fig. 4. p; and Plate II, fig. 1. p. Crenulated margin. ‘That fine notched edge of shells, which unite into notches in the opposite valve, as genus Donax. Plate IV. fig. 6. m m. Striz are fine thread-like lines, generally on the exterior surface of shells, and are sometimes both longitudinal and transverse. When the strie of shells appear indistinct, as if worn out, it is termed obsolete striz. In some instances the insides of shells are striated; for example, the Fasciolaria tulipa. The character of the striz is often of much use in distinguishing species. Plate II. fig. 2. f. Right Valve, is that valve which, when viewed with the inside uppermost has the anterior slope pointing to the right hand. Plate I. fig. 8; and plate 4. fig. 5. and 6. 0. Left Valve. The opposite of the above; the anterior slope points to the left hand, when viewed from the inside. Plate IV. fig. 3, 6,7, 9, &e: Length of the Shel! is taken from the ligament, or the beak, to the opposite margin. For example, Mytilus: it is longer than it is broad, and the solens are broader than long. Plate I. fig. 5, uu. and Plate Il. fig. 4. uu. Breadih is measured from the most extreme edge of the ante- rior and posterior slopes, being in a contrary direction from its Q* 14 ry INTRODUCTION. length. Many shells are broader than long, such as most of the Myz, Solene, Telline, &c.; and the Mytilus, Ostrea, Pinna, &c. are in general longer than broad. Plate I. fig. 5.vv. Plate II. fig. 4. uv. ; Byssus, or beard, is an appendage composed of filaments of a silky texture, by which some of the Bivalves fasten themselves to their beds, such as the Mytilus, Pinne, &c. Plate Il. fig. 6. s. 2 UNIVALVE. re The shells called univalve, or those composed of one part oniy, are far more numerous than the two preceding, both in genera and species; and it requires a considerable degree of attention to discriminate many of the sfecies, as they run into each other so much; and they are divested of the strong and distinct character afforded by the teeth of bivalves; besides many of the species there are several varieties. ' In the examination of shells of this order, the general contour or outline of the whole shell is the first particular to be attended to, as this leads to those distinctions necessary in the definition of simple, spiral, or turbinated shells, Univalves with a regular spire, and those without a regular spire. ‘The genera of this order are formed principally from the shape of the aperture, taken in con- junction with the general shape of the shell; from the spire being lengthened or depressed, being with or without a canal, the length of the beak and its direction, together with the particular form of the outer lip: the colour of shells only serves as a specific distinction, and cannot in this respect, in all cases, be depended upon, although in others it is an unvarying test. The particular manner in which the spots are disposed, frequently characterises species. | Apex. The summit, tip, or highest part of the spire. Plate II. fig. 7,8, 9..44 A. Base is the opposite extremity from the apex, or tip of the spire. Tn shells with a beak it implies the tip of such beak; Plate II. fig. 11. B. In shells without a beak it is understood to be the lower part, as before-mentioned, opposite the apex; Plate II. fig. 8. EXPLANATION OF THE PARTS OF SHELLS. ~— 15 and 9. B B. In the Patella and some others, the base of the shell is that part on which it rests when it is laid on its mouth, In the Dentalium and Teredo it is the wider end. Body of the shell is the first or lower whorl of the spire, in which the aperture is situated, and is in general longer than the remaining whorls. Plate II. fig, 10 and 12. F F. and Plate III. fig. 7 and 9. .F F. Front of the shell is that side where the aperture is situated. Plate Il. fig. 7. J; and Plate III. fig. 8, J. Back is the opposite side to that in which the aperture is placed or turned directly from the observer. Plate III. fig, 5. and 10. G G. The venter, or belly, is the most prominent part of the lower whorl or body, generally situated in the vicinity of the lip over the aperture; and formed by the convexity of the aperture. It is in general only made use of in describing shells whose body is large in proportion to the size of the spire. Plate III. fig. 5 and 10. Hi. Sides. The extreme edges of the shell, when viewed either in front or from the back. Plate II. fig. 11. KK KKKEKK K, Right side is, when the shell is viewed in front that side next the observer’s left hand. Left side, the side with the aperture in it. Aperture, or mouth, is that part of the lower whorl or body by which the animal protrudes itself. This is one of the principal generic distinctions of Univalve shells, and differs very much in shape ; some apertures being rounded, others semilunar, angular, &c. - Plate II. fig. 9 and 11. C C3; and Plate III. fig, 1, 3, and 14. C CC. Some apertures have a canal at their base, and others are devoid of it. In various genera it extends the whole length of the shell, as in the Cyprea, and some of the Cones with depressed spires. This in several individuals is either entirely open, or is clused by an operculum or lid, which is usually affixed to the foot of the animal. Canal, or gutter, is the inside of the elongations of the aper- ture, or both lips of the shell of those species with a beak in which it forms a concave channel or gutter, running from its 16 INTRODUCTION. commencement in the aperture to the extremity or base, Plate Il. fig. 10 and 11. Q Q. Plate III. fig. 8. Q. Some species are furnished with two canals, one situated at the junction of the outer lip and body, asin the Murex. Beak, is that lengthened process in which the canal is situate ; it commences a little higher up, on the outside, than the insertion of the canal in the inside, which is always distinctly marked by the line of the aperture. Plate II. fig 11. ». This process is not so conspicuous in some of the species of Voluta, but is more marked in the genera Murex, Fusus, Pyrula, &c. Pillar, or columella, is that process which runs through the centre of the shell in the inside from the base to the apex in most univalve shells, and appears to be the support of the spire : and, indeed, seems to form that part of the shell: it is in general grooved or folded ; but, as it is situated in the interior of the shell, a minute description is unnecessary. Plate II. fig. 10 and 12. M M MM M.; and plate Ill. fig. 9. MMM. The internai edge of its base is frequently described as having plaits, &c. Plaited Columella are those folds, or plaits, which are the dis- tinguishing characteristic of the Volute and other genera. Plate Inte. 1. =; Pillar Lip is a continuation of the glossy process with which the aperture is lined, and expanded on the columella. Plate III. figures 7 and 8. O O. This is termed the inner lip by some authors. Outer Lip. The expansion, or continuation of the body of the shell on the left margin of the aperture, and is also lined with the glossy process of the aperture. Plate II. fig. 7. W; and Plate ITI. fig. 8. WW AN. The latter is an example of the alated or winged shells. Operculum, or lid. This is only an appendage to the turbi- nated or spiral shells affixed to the foot of the animal, sometimes of a testaceous, in others of a horny or cartilaginous substance. It acts as a door or lid, and is calculated for the protection of the animal, when it retires within its dwelling, from the intrusion of its enemies, and adapted to the shape of the aperture, which it . EXPLANATION OF THE PARTS OF SHELLS. 17 closes nicely up: as exemplified in the operculum of the Turbo, and is of a hard stony appearance. Plate III. fig. 4. Spire consists of all the whorls of the shell, except the lower one, which, as before observed, is termed the body of the shell. Plate II. fig. 12. D; and Plate III. figures 7 and 8. D D. The spire is a prominent feature of the Univalve; and upon its being elevated, depressed, &c. depends much of the generic and specific definition. Adanson, in his ‘ Natural History of Senegal,’ says that the external character of the spire varies according to the plane they turn upon, which, he observes, is either horizontal, cylindrical, conic, or ovoid. At the same time, he admits that there are a great many intermediate forms which cannot properly be defined. It must be remembered that many of the young shells have not the same nnmber of wreaths. as the adults; from which it would appear, that the part of the animal nearest the apex never increases in size. 'The number of wreaths cannot, at all times, be depended upon. A full grown shell may, however, be known from the outer-lip, which has generally an unfinished appearance in young shells. Indeed, in all the land and fresh water shells it is a distinct criterion, as they are never complete in the form of the outer-lip till full grown. Worl is one of the wreaths or volutions ofthe shell. Plate Il. fig. 8. Z; and Plate IIT. fig. 10. LZ. Depressed Spire is when the spire is very flat, as in the shells of the genus Planorbis, &c. Pl. I. fig. 12. d; and PI. Ill. fig. 5. s. A flat. shell is figured in Plate III. fig. 14. Involuted Spire, those shells which have their whorls, or wreaths, concealed in the inside of the first whorl or body, as in some of the Nautili and Cypre. Suture of the Spire, or whorls, is a fine spiral line, which sepa~ rates the wreaths or whorls from each other ; it is sometimes crenu- lated, undulated, or sulcated, and not unfrequently elevated or projecting. Plate II. . e. Reversed, or Heterostrophe Spire, is when the volutions of the spire revolve in the same manner as a common corkscrew, or when the aperture is placed downwards, the nature of the 18 INTRODUCTION. spire runs upwards from the right hand to the left, Plate III. fig. 13. In some of the more depressed species of Helix, or Nautilus, great attention is