Part 16

LUTRARIA. Auct. (_Lutum?_ mud.)--_Fam._ Mactracea, Lam.--_Descr._ Thin, equivalve, inequilateral, transverse, oblong or ovate, gaping at both extremities; hinge with one double and sometimes one single cardinal tooth in each valve, and a triangular, oblique pit with a prominent margin, containing the ligament; muscular impressions distant; palleal impression having a large sinus.--_Obs._ This genus differs from Mactra in the entire absence or indistinctness of lateral teeth. Fig. 77, L. Papyracea. (Ligula, Leach.) Fig. 78. L. Solenoides. Sandy and muddy shores.

LUTRICOLA. Bl. LUTRARIA. Lam. Fig. 77, 78.

LYCOPHRIS. Montf. A microscopic fossil described as resembling NUMMULITES, but having a granulated surface.

LYMNADEA. Sw. A sub-genus of "Mysca," Turton, in the family of Nayades, Lam. thus described: "Posterior hinge margin elevated and winged; the valves connate; the surface smooth. L. alata. _Sw._ _Ex._ Conch. (fig. 48.) fragilis. _Sw._ Zool. Ill. compressa, _Lea._ Am. Tr. iii. pl. 12. f. 22." Sw. p. 379.

LYMNEA. See LIMNEA.

LYMNEUS. Lam. See LIMNEANA.

LYONSIA. Turt. Inequivalve species of ANATINA, Auct. which have no spoon-shaped cavity in the hinge, but an accessary piece. L. striata, fig. 491, 2.

LYRODON. Goldf. TRIGONIA?

MACLURITES. Lesuour. Journ. des Scienc. Nat. Philad. t. 1. p. 312. pl. 13. fig. 2, 3.

MACOMA. Leach. VENUS tenuis, Bl. and similar species, described as "Clothed with an epidermis; striated, compressed, oval; the summits not very prominent; two bifid teeth upon the right valve and a single undivided one upon the left."

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

MACROSPIRA. Guild. A genus composed of HELIX octona, Auct. Macrospira aperta, Guild.

MACROSTOMATA. Lam. ([Greek: Makros], _macros_, long; [Greek: stoma], _stoma_, mouth.) A family belonging to the first section of the order Trachelipoda, the shells belonging to which are described as haliotoid or ear shaped, with a very large aperture, destitute of an operculum. This family contains the following genera, which maybe thus distinguished.

1. VELUTINA. Globose, with velvety epidermis. Fig. 337.

2. STOMATIA. Ear-shaped; pearly within; including STOMATELLA. Fig. 335, 336.

3. SIGARETUS. The same, not pearly; including _Cryptostoma_. Fig. 334.

4. CORIOCELLA. The same, thin, transparent.

5. HALIOTIS. The same, not thin, nor transparent; with holes; including _Padollus_. Fig. 338, 339.

6. SCISSURELLA. Heliciform, with a slit near the aperture. Fig. 340.

7. PLEUROTOMARIA. Trochiform, with a slit at the edge of the aperture. Fig. 341.

MACTRA. Auct. (_Mactra_, a kneading trough.) _Fam._ Mactracea, Lam. Conchacea, Bl.--_Descr._ Usually thin, equivalve, sub-equilateral, sub-trigonal, slightly gaping at the extremities; hinge with one cardinal tooth, divided into two parts, diverging from the umbo, with sometimes a very small laminar tooth close to its side; a deep triangular pit near the centre, containing the cartilage; one long, lateral tooth on each side of the umbo in one valve, received between two in the other; muscular impressions two, lateral; palleal impression with a small sinus.--_Obs._ This genus contains many species of beautiful shells found in various parts of the world, some are common in Britain. Fossil species are not numerous, they occur in the tertiary strata. Fig. 79 to 82.

MACTRACEA. Lam. A family of the order Conchifera Dimyaria, Lam. Sect. Tenuipedes. The cartilage placed in a trigonal pit with a small external ligament. The genera may be thus distinguished.

1. LUTRARIA. No lateral teeth, shell gaping. The short species constitute the genus _Ligula_. Fig. 77, 78.

2. MACTRA. Lateral teeth, shell closed. This genus has been divided into Mactra, Mulinia, Schizodesma and Spisula, by Mr. Gray. Fig. 79 to 82.

3. GNATHODON. Teeth serrated, thick, one angular. Fig. 83.

4. CRASSATELLA. Shell thick, lateral teeth. Fig. 84.

5. AMPHIDESMA. A distinct external ligament, internal ligament oblique. Fig. 85.

6. ERYCINA. A short tooth on each side of the cartilaginous pit in each valve. Including Mesodesma. Fig. 86.

7. UNGULINA. Ligament flat, divided. Fig. 88.

MACULATED. (From _Macula_, a spot.) Spotted or patched. This term is applied by conchological writers, to those shells which are coloured in spots or small patches. In the same sense it is also used as a specific name. As for instance, Cytherea maculata, fig. 167, c. and Hippopus maculatus, fig. 156.

MAGAS. Sow. ([Greek: Magas], _magas_, a board, a deck.) _Fam._ Brachiopoda, Lam.--_Descr._ Equilateral, inequivalve; one valve convex, with a triangular area, divided by an angular sinus in the centre; the other valve flat, with a straight hinge line and two small projections; a partial longitudinal septum, with appendages attached to the hinge within. Differing from Terebratula in having a triangular disc, and not a circular perforation. Magas pumilus, fig. 299. Fossil in chalk.

MAGILUS. Montf. _Fam._ Cricostomata, Bl. Serpulacea, Lam.--_Descr._ Thick, tubular, irregular, contorted; rounded above, keeled beneath, free; apicial extremity convolute, heliciform, ovate or sub-globose; aperture elliptical.--_Obs._ This shell when in a young state presents the characteristics of a regularly formed spiral univalve, living in holes in madrepores. As the madrepore increases in bulk, the animal gives an eccentric course to the shell, in order to have its aperture even with the surface, and leaving the nucleus or young shell behind, fills it up with calcareous matter to reside in the open extremity of the tube. Fig. 9, 10. Red Sea and Mauritius.

MALACOTA. Schum. OTION. Leach.

MALACOZOA. Bl. ([Greek: Malakos], _malacos_, soft; [Greek: Zôon], _zoon_, animal.) The type or general appellative in De Blainville's system, including all molluscous animals, excepting those with multivalve shells.

MALDANIA. Lam. The second family of the order Annelides Sedentaria. The only genus of shells described in this family is Dentalium, fig. 2, to which may be added Pharetrium, König. fig. 3. It is doubtful however whether the latter do not belong to an unknown genus of Pteropodous Mollusca.

MALEA. Valenciennes. A genus composed of DOLIUM latilabrum, Kiener, and other similar species.

MALENTOZOA. Bl. ([Greek: Malakos], _malacos_, soft; [Greek: en], _in_, [Greek: temnô], _temno_, cut; [Greek: Zôon], _zoon_, animal.) Or articulated mollusca. The sub-type in De Blainville's system, comprehending those with multivalve shells.

MALLEACEA. Lam. A family belonging to the order of Conchifera Monomyaria. Containing the following genera of irregular pearly bivalves.

1. AVICULA. Hinge linear, simple, including _Meleagrina_. Fig. 163, 164.

2. PERNA. Hinge with linear grooves, including _Pulvinites_. Fig. 166, 170.

3. GERVILLIA. Shaped like Modiola, with irregular grooves. Fig. 162.

4. CRENATULA. Hinge with a series of pits. Fig. 168.

5. CATILLUS. Like Perna, but more regular and convex. Fig. 167.

6. MALLEUS. A triangular disc on the hinge, and two auricles. Fig. 165.

MALLEUS. Auct. (_Malleus_, a hammer.) _Fam._ Malleacea, Lam. Margaritacea, Bl.--_Descr._ 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. It belongs to the Linnæan genus Ostrea, from which it differs in being attached by a byssus. Fig. 165, M. Vulgaris. Tropical.

MAMILLARIA. Sw. A sub-genus of NATICA, corresponding with Polinices of Montfort, having the spire small and the umbilicus filled. _Ex._ Natica Mamilla, Auct. fig. 327.

MAMMILLATED. (_Mammula_, a little teat.) A term applied to the apex of a shell when it is rounded like a teat. _Ex._ Voluta Vespertilio, fig. 433.

MARGARITA. Leach. (_Margarita_, a pearl.) A genus of small shells resembling the genus Trochus, from which it differs in having an operculum consisting of few whorls. M. tæniata, fig. 362. Mr. G. B. Sowerby, sen. has enumerated 15 species in a list accompanying the figures published by the author of this manual in Nos. 132 to 134 of his Conchological Illustrations.

MARGARITACEA. Bl. The third family of Lamellibranchiata, Bl. The shells belonging to it are described as irregular, inequivalve, inequilateral, black or horny without, pearly within; hinge auriculated, scarcely developed, and without teeth. The ligament is variable and there is a large sub-central muscular impression. This family contains the genera Vulsella, Malleus, Pinna, Crenatula, Inoceramus, Catillus, Pulvinites, Gervillia and Avicula.

MARGARITACEOUS. (_Margarita_, a pearl.) Pearly.

MARGARITANA. Schum. A sub-genus of Uniones, composed of species having "one cardinal tooth." ALASMODON, Say. MYA Margaritifera, Linn.

MARGARITIFEROUS. (_Margarita_, pearl; _fero_, to bear.) Pearl-bearing. Applied to shells which form pearls; as Meleagrina Margaritifera, or Pearl-bearing Oyster.

MARGINAL. Near the margin or edge.

MARGINATED. (_Margo_, edge.) Having an edge or border thicker than the rest of the shell, from which circumstance the little genus Marginella derives its name.

MARGINELLA. (A little rim or border.) _Fam._ Columellaria, Lam. Angyostomata, Bl.--_Descr._ Ovate, smooth, shining, with a short, sometimes hidden spire; aperture narrow, emarginated; columella with several oblique folds; outer lip neatly reflected.--_Obs._ This genus of pretty little shells differs from Voluta, in the reflection of the outer lip. The animal covers the greater part of the shell with the mantle, and by continually depositing vitreous matter gives it a bright polish, which, together with the delicately neat arrangement of colours in most species, renders them exceedingly beautiful. The Marginellæ are marine and tropical. A few fossil species are found in the Calc-grossier. Fig. 437. M. Glabella. GLABELLA, Sw.

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

MARINE CONCHACEA. See CONCHACEA.

MARINE TESTACEA. Those shell-fish which inhabit seas, lakes, &c. of salt water, in distinction from the _Aquatic_ Testacea, or those which are found in rivers, ponds or stagnant pools of fresh water: and also from the _Land_ Testacea, which live on land and breathe air. The great proportion of shells belong to the former class, those of the latter two classes being limited in their number, and in the genera to which they belong.

MARINULA. King. A genus of small shells resembling Auricula and Pedipes, described as "Ovate, sub-solid, with aperture ovate entire; columella bidentate, uniplicated towards the base, with large sub-remote teeth; the largest uppermost; no operculum."

MARMAROSTOMA. Sw. A genus of "Trochidæ," Sw. thus described: "Umbilicus deep; spire of few whorls, much depressed, and obtuse; inner lip obsolete; base even more produced than in _Senectus_, but never distinctly channeled. M. versicolor. Mont. 176. f. 1740, 1741, undulata. Chem. 169. f. 1640, 1641," Sw. p. 348.

MARPESSA. Gray. A sub-genus of Clausilia, C. bidens, &c. Auct. Gray's Turton, p. 212.

MARTESIA. Leach. A genus composed of those species of PHOLAS, Auct. which are described as short, cuneiform, nearly closed at both extremities, having several accessary pieces on the middle of the back, and two marginal, lower down.

MEASUREMENT. The most approved method of stating the measurements of various kinds of shells is as follows: _symmetrical convolute univalves_, the length is from anterior to posterior; the depth from ventral to dorsal; the breadth, from side to side of the aperture. Of _symmetrical conical univalves_, length, from front to back; breadth from side to side; depth from apex to base. Of _spiral univalves_, length, from apex to anterior of the columella or axis of the shell; breadth, across from the outer lip to the opposite side. Of _non-symmetrical bivalves_, the length is from the anterior to the posterior margin; breadth, from the greatest convexity of one valve to the corresponding part of the other; depth, from the ventral to the dorsal margin.

MEGADESMA. Bowd. ([Greek: Megas], _megas_, great; [Greek: desma], _desma_, ligament.) POTAMOPHILA, Sow. GALATHÆA, Lam.

MEGADOMUS. Sw. A sub-genus of Unio, thus described: "Only one lateral tooth in each valve; cardinal teeth two; posterior hinge margin winged. M. gigas, _Sw._" Sw. p. 378.

MEGALODON. Sow. ([Greek: Megas], _megas_, great; [Greek: odos], _odos_, tooth.) _Fam._ Cardiacea, Lam.--_Descr._ Equivalve, longitudinal, acuminated at the umbones, thick; hinge forming an incrassated septum across the cavity of the shell, with a large bifid tooth in the right valve, and one irregular and one pointed in the left; ligament long, external.--_Obs._ The general form, the thickened hinge reaching across the cavity of the valve and the terminal umbones serve to distinguish this genus from Cardita, to which, however, it is nearly allied. M. cucullatus, fig. 127.

MEGALOMASTOMA. Guild. A sub-genus of Cyclostoma, thus described: "Cylindrical, resembling _Pupa_, but has a horny operculum; spire not thickened; teeth or fold on the pillar none, flavula _Sw._ En. Méth. 461. f. 6, brunnea _Guild._ (_fig. 97. g. h. 1._)" Sw. p. 336. Mr. Gray applies the name to those species which have "a groove or ridge in front of the mouth near the pillar."

MEGARIMA. Rafinesque. A genus proposed to include species of TEREBRATULA, Auct. which are smooth and nearly equivalve. T. lævis, T. crassa, T. truncula.

MEGASPIRA. Lea. ([Greek: Megas], _megas_, great, and spire.) M. Ruschenbergiana, (fig. 294) is a pupiform land shell remarkable for the length of its spire, which consists of no less than twenty-five close set, narrow, gradually increasing whorls. The outer lip is simple, slightly thickened; the inner lip has a tooth on the body-whorl, and two folds on the columella. Only one species of this singular shell is known.

MEGATREMA. Leach. A genus composed of those species of Pyrgoma, Auct. which have a large aperture. Fig. 33.

MELACANTHA. Sw. A sub-genus of Melania. Sw. p. 341.

MELAFUSUS. Sw. A sub-genus of Melanopsis. Sw. p. 341.

MELAMPUS. Montf. CONOVULUM, Lam. A genus composed of species of AURICULA, Auct. of a conical form. A. conoidalis, fig. 298.

MELANIA. Auct. ([Greek: Melas], _melas_, black.) _Fam._ Melaniens, Lam. Ellipsostomata, Bl.--_Descr._ Turrited; spire generally elongated, acute; aperture entire, oval or oblong, pointed at the posterior extremity, rounded anteriorly, with a kind of indistinct canal or sinuosity: epidermis thick, generally black.--_Obs._ In common with other fresh-water shells, the Melaniæ are frequently found with corroded apices. This genus is known from Melanopsis by the absence of the notch at the anterior part of the aperture. The Melaniæ occur in rivers of warm climates. The fossil species are frequent in upper marine formations. Fig. 313, M. subulata.

MELANIANA. Lam. (Melaniens.) A family belonging to the first section of the order Trachelipoda. The genera contained in it maybe distinguished as follows.

1. MELANOPSIS. Aperture notched; columellar lip thickened above; including _Pirena_. Fig. 315, 316.

2. MELANIA. Aperture not notched; columellar lip not thickened; including _Auculosa_, _Pasithæa_, _Io_. Fig. 313, 314, 317.

MELANITHES. Sw. A sub-genus of Melanopsis. Sw. p. 341.

MELANOIDES. Olivier. MELANOPSIS. Fer.

MELANOPSIS. Fer. _Fam._ Melaniana, Lam. Entomostomata, Bl.--_Descr._ Oval or oblong, fusiform; spire acute, sometimes elongated; aperture oblong or oval, pyriform, with a distinct notch at the anterior extremity; columella tortuous, callous, thickened at the extremity near the spire; epidermis thick, horny, generally black. Subtropical.--_Obs._ This description includes the two first species of the genus Pirena, Lam. The Melanopsides are known from the Melaniæ by the notch in the aperture. Fig. 315. M. costata.

MELAS. Montf. MELANIA, Auct.

MELATOMA. Sw. A sub-genus of Melanopsis. Sw. p. 341.

MELEAGRINA. Lam. MARGARITA. A genus composed of the Pearl Oyster and similar species, separated from Avicula on account of the roundness of their general form, but re-united by Sowerby. For generic characters, see Avicula. Fig. 164. M. margaritifera.

MELEAGRIS. Montf. TURBO Pica, Auct. and similar species, having the aperture oblique, the columella gliding imperceptibly into the outer lip, and having an umbilicus.

MELINA. Schum. PERNA, Auct.

MELO. Brod. (_Melo_, a melon.) _Fam._ Columellaria, Lam.--_Descr._ Light, ventricose, oval, with a light greenish brown epidermis, spire short, papillary, regular, sometimes hidden by the last whorl; aperture large, nearly as long as the whole shell, emarginated anteriorly; outer lip thin; columella slightly curved, with four or five laminar, oblique, prominent plaits.--_Obs._ The genus Melo has been separated from _Voluta_ principally on account of the largeness of the aperture, the lightness of the shell and the thinness of the outer lip. Melo differs from Cymba in the regularity of the spiral apex, and in the greater rotundity of the shell. The Melons are beautifully coloured large shells, found in the seas of the old world. The Melo Indicus has a certain resemblance to a Melon. Fig. 435. M. Æthiopicus.

MELONIA or MELONITES. A genus of microscopic Foraminifera.

MERCENARIA. Schum. VENUS Mercenaria, Auct. The Money shell which passes current for cash, under the name "Wampum," among the North American Indians.

MERETRIX. Lam. Original name for Cytherea, Lam.

MEROE. Schum. CYTHEREA Meroe, sulcata, scripta, hians, Auct. and similar species. Fig. 117, a.

MESODESMA. Desh. ERYCINA, Lam. according to G. B. Sowerby.

MESOMPHYX. Rafinesque. A genus proposed to be separated from HELIX, Auct.

MICROTOMA. Sw. A genus of "Purpurinæ," Sw. thus described, "Pillar very broad and curving inwards; aperture effuse; the notch at the base small and nearly obsolete; spire very short, patula. Mart. 69. f. 758, 759. persica. En. Méth. 397. f. 1. unicolor. _Sw._ Chem. f. 1449. Sw. p. 301." Purpura Persica. Fig. 414.

MILIOLA. Lam. A genus of microscopic Foraminifera.

MISILUS. Montf. A genus of microscopic Foraminifera.

MITRA. Lam. (_Mitre._) _Fam._ Columellaria, Lam. Angyostomata; Bl.--_Descr._ Oblong, thick, covered with a light brown epidermis; spire long, turrited, acute; aperture emarginated anteriorly; outer lip thickened; columella with several oblique, thick plaits.--_Obs._ The pretty small shells composing this genus differ from Marginella, not only in general form, but in the outer lip not being reflected. Some species of Voluta, of a more elongated shape than the rest, present a near approach to the most ventricose of the Mitræ. The apex of Mitra, however, is always acute, while that of Voluta is generally papillary. The aperture of the former is narrow and the inner lip thickened, the contrary being the case with the latter. The shells of this genus are varied in colouring which is generally rich; and also in form, some being angulated, some plicated, some coronated and others smooth. The species are mostly tropical; very few occur so far north as the Mediterranean. Fossil species are numerous in the Eocene beds. Fig. 431. M. Plicaria. Fig. 432. Conohelix marmorata, Sw.

MITRELLA. Sw. A genus consisting of MITRA Fissurella, casta, Olivæformis, and similar species, described as "Rather small; olive-shaped; unequally fusiform; always smooth and polished, and sometimes covered with an epidermis; base obtuse and effuse; spire nearly or quite equal to the aperture; plaits of the pillar few, oblique, and extending beyond the aperture, which is smooth internally." Sw. p. 321. M. Fissurata, E. M. 371. f. 1. Olivarii, f. 2. Dactylus. 372. f. 5. _Ex._ Mitra bicolor.

MITREOLA. Sw. A genus of "Mitranæ," Sw. thus described: "Small; unequally fusiform; the base obtuse; inner lip, typically thickened, inflected, and either toothed or tuberculated; plaits on the pillar distinct, the inferior largest; tip of the spire sometimes papillary; aperture without either striæ or groove." Sw. p. 320, M. Monodonta, M. Terebellum. Zool. Illustr. II. 128. f. 1. f. 2.

MODIOLA. Lam. (_Modiola_, a little measure.) _Fam._ Mytilacea, Lam.--_Descr._ Equivalve oblique, cuneiform, inequilateral, thin, with the anterior side short and narrow, slightly gaping to admit the passage of a byssus, and the posterior side elongated, broad, sub-quadrate; hinge thin, toothless, rectilinear, with a long, partly external ligament; muscular impressions two in each valve; palleal impression irregular, not sinuated.--_Obs._ This genus differs from Mytilus, to which the common muscle belongs, in the anterior margin being rounded out beyond the umbo, which in Mytilus is terminal. The Lithodomi may be known from this genus by their cylindrical form. Fig. 160, M. Tulipa.

MOLLUSCA. (From _Mollis_, soft.) The twelfth class of invertebrated animals with univalve shells or none; divided into the following orders: Pteropoda, Gasteropoda, Trachelipoda, Cephalopoda, Heteropoda, fig. 220 to 488. The term mollusca is also used in a general sense to include the classes Conchifera and Mollusca of Lamarck, corresponding with the type Malacozoa of De Blainville.

MONEY COWRY. Cypræa Moneta, which passes current in some parts of Africa and the East Indies.

MONILEA. Sw. A sub-genus of Monodonta. Sw. p. 352.

MONOCEROS. ([Greek: Monos], _monos_, single; [Greek: Keras], _ceras_, horn.) _Fam._ Purpurifera, Lam.--_Descr._ Ovate, thick, covered with a brown epidermis; spire short, consisting of few whorls; aperture emarginated anteriorly; columella rather flat; outer lip thick, with a prominent tooth near the extremity.--_Obs._ This genus resembles Purpura, in every respect, except in having the tooth from which the name is derived. A catalogue of 16 species by Mr. Sowerby, sen. is published with figures of 14, in parts 58 to 67 of the Conchological Illustrations by the author. The species belong to the South American coasts of the Pacific Ocean.

MONOCONDYLÆA. D'Orb. A sub-genus of Uniones, described as equivalve, inequilateral, sub-rotund or angulated; hinge consisting of a large, obtuse, round cardinal tooth in each valve, with no lateral teeth. Monocondylæ (Unio) Paraguayana, D'Orb. fig. 149.

MONODONTA. Lam. ODONTIS, Sow. A genus separated from Trochus, Auct. on account of the tooth or notch with which the columella abruptly terminates. M. labeo, fig. 366.