Part 15

LABIUM, or inner lip,--is used to express that side of the aperture which is nearest to the axis and generally contiguous to the body whorl. The lower part of this, when sufficiently distinct from that part which overwraps the body whorl, is called the Columella.

LABRUM, or outer lip,--is the edge of the aperture at the greatest distance from the axis.

LACINEA. Humph. CHAMA, Lam.

LACUNA. Turt. _Fam._ Turbinacea, Lam.--_Descr._ Globose, thin, covered with a smooth epidermis; spire short, consisting of few rapidly increasing whorls; aperture semilunar, rounded at the extremities; columella oblique, reflected over part of the umbilicus; umbilicus forming a lengthened area behind the columella. Northern shores. Fig 364, L. Pallidula.

LAGENULA. Montf. A genus of microscopic Foraminifera.

LAMELLATED. (_Lamella_, a thin plate.) When the layers of which a shell is composed, instead of being compacted into a solid mass, are separated, overlying each other in the manner of tiles, with the edges prominent, the structure is said to be lamellated or foliaceous.

LAMELLIBRANCHIATA. Bl. The third order of the class Acephalophora, Bl. consisting of bivalve shells, divided into the families Ostracea, Subostracea, Margaritacea, Mytilacea, Polydontes, Submytilacea, Chamacea, Conchacea, Pylorides, Adesmacea.

LAMELLIPEDES. Lam. (_Lamella_, a thin plate, _pes_, a foot.) The third section of the order Conchifera Dimyaria, containing bivalves, with the foot of the animal broad and thin; divided into the families Conchacea, Cardiacea, Arcacea, Trigonacea, Nayades. Fig. 111. to 152.

LAMPAS. Montf. LENTICULINA, Bl. A genus of microscopic Foraminifera.

LAMPRODOMA. Sw. A genus of "Olivinæ," Sw. thus described:--"Mitriform; spire produced, conic; resembling MITRELLA in shape, but the suture is channelled; the aperture effuse at the base, contracted above; lower half of the pillar with 6 to 7 plaits. Volutella, Zool. Ill. ii. series, pl. 40. f. 1. (_fig. 86._ )" Sw. p. 321.

LAMPROSCAPHA. Sw. A sub-genus of "Anodontinæ," Sw. thus described:--"Shell not winged, elongate, pod-shaped; teeth none; bosses near the anterior extremity. Tropical America only? L. ? elongata. _Sw._ Zool. Ill. i. 176. ensiforme, _Spix._ Braz. Test. siliquosa. Braz. Test. pygmæa. Ib." Sw. p. 381.

LAMPROSTOMA. Sw. A sub-genus of Canthorbis (Trochus), described at p. 350, Lardn. Cyclop. Malac.

LAMPUS. Humph. TEREBRATULA, Lam.

LANCEOLATE. Lengthened like a lance.

LANISTES. Montf. Reversed species of AMPULLARIA, fig. 319.

LAPLYSIA. See APLYSIA.

LAPLYSIACEA. Lam. (properly Aplysiacea) A family belonging to the first section of the order Gasteropoda, Lam. containing the genera Aplysia and Dolabella. Fig. 254, 255.

LARVA. Humph. FISSURELLA, Lam.

LATERAL. (_Latus_, a side.) The lateral teeth are those which, taking their rise near the umbones, proceed to some distance towards the sides of the shell; as distinguished from the cardinal teeth, which receive their full developement close to the umbones. Lateral muscular impressions are those which are placed at a distance from each other, on the opposite sides of the shell.

LATIAXIS. Sw. A genus of "Eburninæ," Sw. corresponding with the genus Trichotropis. Sow. (Sw. Malac. p. 306.)

LATIRUS. Montf. A genus composed of species of FUSUS, Auct. which have an umbilicus and are turriculated.

LAURIA. Gray. A sub-genus of PUPA, containing P. umbilicata, &c. (Gray's Turton, p. 193.)

LEGUMINARIA. Schum. A genus composed of species of SOLEN, Auct. which have an internal longitudinal bar or rib. Fig. 61. S. Radiatus, Lam.

LEILA. Gray? Described as having the hinge edge smooth like Iridina, but having a "sharp siphonal inflexion." (Syn. B. M. p. 142.)

LEIODOMUS. Sw. A genus of "Buccininæ," Sw. consisting of Terebra vittata and other similar species. This genus corresponds with Bullia, Gray.

LEIOSTOMA. Sw. A genus of "Fusinæ," Sw. thus described, "Equally fusiform," (with Fusus) "but ventricose in the middle; shell entirely smooth, almost polished; inner lip thickened, and vitreous; base of the pillar very straight. Fossil only. (_fig. 75._) L. bulbiformis. En. Méth. 428. f. 1."

LEMBULUS. Leach. A genus composed of oval species of NUCULA, resembling N. margaritacea, fig. 137.

LENDIX. Humph. PUPA, Lam.

LENGTH. See MEASUREMENT.

LENTICULAR. (_Lens._) Of a circular, convex form, as Pectunculus, fig. 134.

LENTICULINA. Lam. A genus of microscopic Foraminifera.--_Descr._ Lenticular, sub-discoidal, compressed, convolute, symmetrical; aperture notched; chambers few in number; visible on the exterior, radiating from the centre of the disk.

LEPADICEA. Bl. The first family of the class Nemantopoda, Bl. This family consists of the same animals which constitute the Pedunculated Cirripedes of Lamarck, and part of the genus Lepas in the system of Linnæus. It contains the genera Gymnolepas, Pentalepas, Polylepas and Litholepas.

LEPAS. ([Greek: Lepas], _lepas_, a rock.) The Linnæan name Lepas contains all the Cirripedes or Multivalves, the different kinds of which are not distinguished in the accounts given by early writers of the habits of the animals. (Fig. 14 to 43.) It was formerly applied to the Limpets or Patella. In fact, the ancient definition was "Concha petræ adhærens," and would apply to any shells attached to rocks.

LEPTÆNA. Dalman. A genus belonging to the Brachiopoda; and thus described:--"Hinge compressed, rectilinear, frequently exceeding the width of the shell." It forms part of the genus Producta, Sow. Fig. 206, L. depressa.

LEPTOCONCHUS. Rüppell. ([Greek: Leptos], _leptus_, thin; [Greek: Konchos], _conchos_, shell.) This shell resembles a young MAGILUS in general appearance, although the animal is said to differ. In the young Magilus also, the inner lip is reflected over the body whorl, which is not the case in Leptoconchus. Red Sea. Fig. 11.

LEPTOCONUS. Sw. A sub-genus of Conus, consisting of Conus grandis, amadis, duplicatus, Australis, &c. Sw. p. 312.

LEPTOLIMNEA. Sw. A sub-genus of Limnea, described as being nearly cylindrical. Limnea elongata, Sow. Gen. fig. 6.

LEPTON. Turton. SOLEN Squamosus, Montague, and other species described as "flat, nearly orbicular, equivalve, inequilateral, a little open at the sides. Hinge of one valve with a single tooth, and a transverse linear lateral one on each side; of the other valve, with a cavity in the middle and a transverse deeply cloven lateral tooth each side, the segments of which divaricate from the beak." To represent this genus we have figured L. Squamosum in the plates, fig. 62. British.

LEPTOSPIRA. Sw. A sub-genus of Bulinus, thus described: "Spire excessively long, sub-cylindrical; body whorl largest; outer lip thickened; aperture oval; no teeth, striata, _Sw._ Chem. 135. f. 1226. signata _Sw._" Sw. p. 335.

LEUCOSTOMA. Sw. A genus of "Achatina," Sw. described as resembling Achatinella, but having a "thick pad" at the top of the "upper lip," and another over the base. L. variegata, Sw. Lardn. Cyclop. Malac. fig. 24. p. 172.

LEUCOTUS. Sw. A sub-genus of Natica, described as intermediate between Sigaretus and Lacuna. SIGARETUS _cancellatus_, Lam. (Sw. Malac. p. 346.)

LICIUM. Humph. OVULA, Lam. (Ovulum.)

LIGAMENT. (From _Ligo_, to bind.) The true ligament is always external, and serves the purpose of binding the two valves of a shell together externally by the posterior dorsal margins. There is another substance, called by Gray the _Cartilage_, which is elastic and of a condensed fibrous structure, placed within the ligament, either close to it, or at a more interior part of the shell; it is sometimes contained in a pit, formed for its reception, in the centre of the hinge. This substance, being elastic, keeps the valves open, unless drawn together by the counteracting force of the adductor muscles. When conchologists speak of a shell as having the ligament external, the real meaning is that these two substances are so close together as in appearance to constitute one body placed outside the shell so as to be seen when the valves are closed. When two ligaments are spoken of, as in Amphidesma, the meaning is that the cartilage occupies a separate place on the hinge.

LIGAMENTIFEROUS. (_Ligamentum_, a ligament, _fero_, to bear.) Having or containing the ligament, as the cardinal pit in Mya, fig. 71.

LIGULA. Leach. A genus containing the more rounded and less gaping species of LUTRARIA, Auct. Fig. 77, Lutraria Papyracea.

LIGULATE. (_Ligula_, a slip, a shoe-latchet.) Thin, slender, like a slip, or neck of any thing, as the anterior muscular impression of Lucina, fig. 104.

LIGUMIA. Sw. A sub-genus of Unio, thus described:--"Very long and pod-shaped; bosses depressed; cardinal teeth moderate. S. recta. Lam. vi. 1. p. 74." Sw. p. 378.

LIGUUS. Montf. A genus containing species of ACHATINA, Auct. which have rounded apertures and lengthened spires, differing from his POLYPHEMI, which have lengthened apertures. A. virginea, Auct. fig. 286, is the type of this genus.

LIMA. Brug. (_Lima_, a file.) _Fam._ Pectinides, Lam. Subostracea, Bl.--_Descr._ Equivalve, inequilateral, compressed, oblique-auriculated, oval, radiately ribbed or striated, imbricated, covered with a light brown epidermis; hinge with a triangular disc between the umbones, divided in the centre by a triangular ligamentary pit without teeth; muscular impression one, sublateral, sub-orbicular.--_Obs._ The shells thus described are marine, two or three species being found on our coasts, and fossil species occurring in Lias, inferior Oolite, Calcaire-grossiér, &c. They differ from Pecten in having a wide hiatus for the passage of a byssus, by which they are occasionally attached, and also in the triangular disc, which separates the umbones. The animal makes use of the valves of his shell as natatory organs, working them like fins or paddles, and by this means proceeding at a rapid rate through the waters. L. Squamosa, fig. 174.

LIMACINA. Cuv. (_Limax_, a snail.) _Fam._ Pteropoda, Lam.--_Descr._ Papyraceous, fragile, planorbicular, sub-carinated, obliquely convolute; spiral side rather prominent, the other side umbilicated; aperture large, entire, not modified, peristome sharp.--_Obs._ This is SPIRATELLA, Bl. The shell figured as Limacina in Sowerby's Genera, under "pteropoda," is an _Atlanta_. Our representation of Spiratella Limacinea, fig. 224. is copied from Blainville.

LIMACINEA. Lam. A family of the order Gasteropoda, Lam. including the following

1. CRYPTELLA. Spire mammillated; a septum. Fig. 256.

2. PARMACELLA. Flat, haliotoid, spiral. Fig. 257, 258.

3. TESTACELLUS. Sub-spiral. Fig. 261.

4. LIMAX. Incomplete. Fig. 259.

5. PLECTROPHORUS. Conical. Fig. 260.

6. VITRINA. Heliciform, hyaline. Fig. 262, 263.

LIMACINEA. Bl. The third family of the order Pulmobranchiata, Bl. Described as containing shells very variable in form, most frequently inclining to globular or oval; the apex always obtuse; aperture variable, but never emarginated. All the Limacinea are phytophagous and terrestrial. This family answers to the genus Helix of Linnæus and to the Colimacea of Lamarck, leaving out the Auriculacea. It contains the genera Succinea, Bulinus, Achatina, Clausilia, Pupa, Partula, Helix, Vitrina, Testacella, Limacella, Limax.

LIMAX. _Lam._ Limacinea, Lam. and Bl.--_Descr._ Internal irregular, sub-quadrate, scutiform, crystalline; apex rounded, indistinct; epidermis, light brown, thin, extending beyond the margin.--_Obs._ The shell is placed under the scutellum of the common garden slug. Fig. 25, L. Antiquorum.

LIMNACEA. Bl. The first family of the order Pulmobranchiata, Bl. The shells of this family are described as thin, with the outer lip always sharp. It contains the genera Limnea, Physa, Planorbis.

LIMNEANA. Lam. A family of the order Trachelipoda, Lam. containing the following genera:--

1. LIMNÆA. Spire produced; including _Physa_. Fig. 308 to 310.

2. PLANORBIS. Spire orbicular; including _Planaria_. Fig. 311, 312.

LIMNEA. Lam. ([Greek: Limnas], _limnas_, lacustrine.) _Fam._ Limnacea, Lam. and Bl.--_Descr._ Oblong, light, thin; spire variable in length, acute; last whorl large, aperture large, longitudinal, entire; inner lip spread over a portion of the last whorl; columella forming an oblique fold; outer lip rounded at each extremity, thin.--_Obs._ These light horn-coloured shells are common in standing pools, ponds and ditches, in various parts of Europe. They resemble the Amber shell (Succinea) in shape, but the animal of the latter is amphibious, and the shell of a bright amber colour. L. Stagnalis, fig. 308. L. auricularia, fig. 309. (RADIX, Montf.) The reversed species have been separated under the name Physa, fig. 310. Other generic names have been given to other species.

LINES OF GROWTH. The concentric striæ or lines formed by the edges of the successive layers of shelly matter deposited by the animal by which it increases the shell. The outer edge of the aperture is always the last line of growth.

LINGUIFORM. (_Lingua_, tongue; _forma_, form.) Tongue-shaped.

LINGULA. Lam. (Dim. from _lingua_, tongue.) _Fam._ Brachiopoda, Lam. Palliobranchiata, Bl.--_Descr._ Equivalve, oblong, depressed, thin, equilateral, gaping and pointed at the umbones, gaping and truncate or trilobate at the opposite extremities, attached by a fleshy pedicule fixed to the umbones.--_Obs._ This is the only bivalve shell which is pedunculated, in which respect it constitutes a singular anomaly. The ancient writers, seeing the valves separate, placed it in their systems under the name Patella Unguis. There are several recent species found in the Moluccas, and some fossils in sandy indurated marl, and in alluvium of Suffolk. L. Anatina, fig. 219, is so named from its resemblance to a duck's bill.

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

LINTHURIS. Montf. Conch. Syst. 2. 154. A genus of microscopic Foraminifera.

LIP. See LABIUM and LABRUM.

LIPPISTES. Montf. A genus of microscopic Foraminifera.

LITHODOMUS. Cuv. ([Greek: Lithos], _lithos_, stone; [Greek: Dôma], _doma_, house.) _Fam._ Mytilacea, Lam.--_Descr._ Transverse, elongated, cylindrical, equivalve, with the extremities rounded, and the posterior extremity rostrated; umbones not prominent, terminal; hinge straight, destitute of teeth; ligament linear, most conspicuous within; muscular impressions two.--_Obs._ The shells composing this genus differ from Modiola, not only in the cylindrical form, but also in the circumstance from which the generic name is derived, i. e. of their living in stones. Thus, while the form and structure of the shell bring it near the Mytili or Muscle shells, the habits of the animal cause it to approach the Lithophagi, or rock-eating molluscs of Lamarck. L. Dactylus (fig. 161,) is the Mytilus Lithophagus of ancient authors.

LITHOLEPAS. Bl. ([Greek: Lithos], _lithos_, stone, [Greek: lepas], _lepas_, rock.) De Blainville's name for LITHOTRYA, Sow.

LITHOPHAGIDÆ. Lam. ([Greek: Lithos], _lithos_, stone; [Greek: Phagô], _phago_, eat or gnaw.) A family of the Conchifera Dimyaria, Lam. consisting of terebrating bivalves, gaping anteriorly, having no accessary valves; and containing the genera Saxicava, Petricola, Venerupis, to which are added other genera enumerated in explanation of figures 91 to 97. Notwithstanding the numerous genera which have been created, I think that the most convenient arrangement will be to reduce them to two, thus--

1. PETRICOLA, with distinct cardinal teeth, including, Clothe, Venerirupis and Coralliophaga. Fig. 91, 92, 97.

2. SAXICAVA, without teeth, including Biapholius, Hiatella, Sphænia, Byssomya, and Thracia. Fig. 93 to 96.

LITHOTRYA. G. B. Sowerby. ([Greek: Lithos], _lithos_, stone; [Greek: truo], _truo_, to bore through.) _Fam._ Pedunculated Cirripedes, Lam.--_Descr._ Eight unequal valves, forming a laterally compressed cone, the lower central valves being very minute; pedicle fleshy, scaly at the upper extremity; fixed at the base in a patelliform shelly support.--_Obs._ This genus derives its name from the power possessed by the animal of making dwelling holes in stones or pieces of rock. The remarkable shelly cups at the base of the pedicle is regarded as analogous to the shelly base of the Balanus, so that this genus would form an intermediate link between the Sessile and Pedunculated Cirripedes of Lamarck. Fig. 39, L. dorsalis. West India Islands.

LITIOPA. Ranz. _Fam._ Turbinacea, Lam.--_Descr._ "Shell not very thick, horny, with a slight epidermis, rather transparent, conical, with whorls somewhat rounded; the last being larger than all the rest together; with the apex pointed, longitudinally grooved; aperture oval, larger anteriorly than posteriorly, with the lips disunited, the right lip simple, separated from the left by a rather indistinct notch, or a slight emargination in the contour. The left lip slightly reflected backwards, so as to form a kind of salient margin with the anterior extremity of the columella, which is united, rounded, arcuated and slightly truncated at the anterior."--_Obs._ The Molluscous animals, whose shells are thus described, are found in the Mediterranean, and are remarkable for the power of suspending themselves from the sea-weed on which they live, by a thread resembling a spider's web. The general appearance of the shell presents a medium between Phasianella and Littorina, but it is apparently destitute of an operculum.

LITTORINA. Fer. (_Littus_, the sea-shore.) _Fam._ Turbinacea, Lam.--_Descr._ Turbinated, thick; spire acuminated, consisting of few whorls, about one third of the axis in length; aperture entire, large, rounded anteriorly; outer lip thickened within, acute; columella rather flattened; operculum horny, spiral, with rapidly increasing volutions.--_Obs._ The shells composing this genus are known from Turbo and Phasianella by the horny operculum; and from Trochus, which has also a horny operculum, by the small number of the whorls. The Littorinæ, among which may be enumerated the common Periwinkle, are, as the name implies, found on sea shores, feeding upon seaweed, in all parts of the world. Fig. 363, _L. Vulgaris_.

LITUACEA. Bl. The second family of Polythalamacea. Bl. The shells are described as chambered, symmetrical, convolute in part of their extent, but constantly straight towards the termination. The genus Spirula, which is admitted into this family, does not properly belong to it, any more than to the Lituolæ of Lamarck, in which it is also placed. It does not agree with the descriptions of either. This family partly corresponds with the "Lituolées," Lam. and contains the genera Lituola, Ichthyosarcolites, Spirula, Hamites and Ammonoceras.

LITUACEA. Lam. A family of the order Polythalamous Cephalopoda, Lam. containing the genus Spirula, fig. 471.

LITUITUS. Montf. SPIROLINA, Lam. Microscopic.

LITUOLA. Lam. A genus of microscopic Foraminifera.

LITUOLÆ. Lam. The third family of Polythalamous Cephalopoda, Lam. the shells of which are described as partially spiral, the last whorl continuing in a straight line. The transverse septa which divide the chambers, are in general pierced by a siphon which breaks itself off before it reaches the succeeding septum. This family contains the genera of microscopic Foraminifera Lituola and Spirolina. The genus Spirula, also placed in this family, does not by any means agree with Lamarck's definitions "the last whorl continuing in a straight line."

LITUUS. Humph. CYCLOSTOMA? Lam.

LIVID. (From _lividus_.) Of a pale, dull, blue colour. The adjective is sometimes used as a specific name. _Ex._ Conus _lividus_, Sanguinolaria _livida_.

LOBARIA. Schum. SANGUINOLARIA rosea, Lam. (fig. 98) and other similar species.

LOBATE or LOBED. Divided into parts.

LOBATULA. Fleming. A genus composed of two very minute species of chambered shells. Serpula lobata and S. concamerata, Mont. Test. Brit. 515.

LOMASTOMA. Rafinesque. An imperfectly defined genus, probably belonging to the Limnacea.

LONGITUDINAL. Lengthwise. Longitudinal striæ, ribs, &c. are those which radiate from the apex and follow the spiral direction of the whorls, in spiral shells; and from the umbo to the ventral margin in bivalves. The term "decourantes" is employed by French conchologists. The bands in Achatina, fig. 286, are longitudinal or spiral.

LORIPEDES. Poli. A genus composed of species of LUCINA, Auct. in which the lunules are not prominent.

LOTORIUM. Montf. A genus composed of species of TRITON, Auct. in which the aperture is effuse. T. Lotorium, fig. 400.

LOTTIA. Gray. PATELLOIDA, Quoy and Gaimard.

LUCERNA. Humph. A generic name applied to some species of Helix included in De Ferussac's sub-genus Helicogena.

LUCERNELLA. Sw. A genus of "Lucerninæ," Sw. thus described: "Teeth on both sides of the aperture; surface regularly and distinctly striated. Circumference convex."

LUCIDULA. Sw. A sub-genus of Lucerna, Humph. thus described: "Aperture transverse, both lips much thickened and united; the outer with marginal obsolete teeth at the base; umbilicus closed. Barbadensis, _Lam._ No. 49. p. 78. Fêr. Moll. pl. 47, 2, 3, 4."

LUCINA. Brug. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._ Equivalve, inequilateral, orbicular, lenticular, radiately striated; hinge with, generally, two minute cardinal teeth, which are sometimes nearly obsolete, and two lateral teeth, on each side of the umbo in one valve, one in the other; ligament external, partly hidden by the margins of the valves when closed. Muscular impressions two in each valve, the anterior one produced into an elongated, ligulate band, the posterior short and semi-rotund; impression of the mantle not sinuated.--_Obs._ The shells of this genus resemble Amphidesma in general form, but are distinguished by the external ligament, the elongated muscular impression, and the want of a sinus in the palleal impression. East and West Indies, and European shores. Fig. 104, L. Tigerina.

LUNULATE. (_Luna_, the moon, dim.) Moon-shaped, having the form of a crescent. Applied most frequently to muscular impressions. Semilunar is sometimes used, perhaps with greater accuracy, to express the same shape.

LUNULE. An impression on the anterior dorsal margin of some bivalve shells. The similar impression on the posterior dorsal margin is called the _escutcheon_.

LUPONIA. Gray. A genus composed of species of CYPRÆA, Auct. which are described as having the anterior of the columellar lip crossed by several irregular ridges, without any distinct marginal ones, internally narrow, flat; the shell pear-shaped, smooth, or cross-ribbed. _Ex._ C. Algoensis, Luponia Algoensis, Gray, fig. 447.