Part 42

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.