A Conchological Manual, George Brettingham Sowerby [little readers .TXT] 📗

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.

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.

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.

 

MELANOPSIS. Aperture notched; columellar lip thickened above;

       including _Pirena_. Fig. 315, 316.

 

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.

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.

 

   MONOICA. Bl. The second sub-class of the class Paracephalophora, Bl.

   divided into the orders Pulmobranchiata, Chismobranchiata,

   Monopleurobranchiata, in the first section; and Aporobranchiata,

   Polybranchiata, Cyclobranchiata, Inferobranchiata, and

   Nucleobranchiata, in the second.

 

   MONOMYARIA. Lam. ([Greek: Monos], _monos_, single; [Greek: muon],

   _myon_, muscle.) The second order of Conchifera, consisting of those

   bivalve shells which have but _one_ principal muscular impression in

   each valve. The Monomyaria are thus divided: First section, containing

   the families Tridacnacea, Mytilacea, Malleacea; second section,

   containing the families Pectinides, Ostracea; third section, containing

   the families Rudistes, Brachiopoda.

 

   MONOPLEUROBRANCHIATA. Bl. The second order of the first section of

   Paracephalophora Monoica. Bl. The animals are described as having the

   lungs branched, situated at the right side of the body and covered more

   or less completely by the operculiform mantle, in which there is

   sometimes enveloped either a flat or a more or less involute shell,

   with a large entire aperture. They have either rudimentary or auricular

   tentacula, or none. This order, which includes mollusca with haliotoid

   or patelliform shells, is divided into the following families: _Fam._

Subaplysiacea; 2. Aplysiacea; 3. Patelloidea; 4. Acera.

 

   MONOPTYGMA. Lea. A genus of small shells resembling Tornatella, but

   having a strong, oblique fold in the centre of the columellar lip. M.

   Elegans, fig. 344.

 

   MONOTHALAMIA. ([Greek: Monos], _monos_, single; [Greek: thalamos],

   _thalamos_, chamber.) The second division of Cephalopoda, Lam.

   containing only one genus, namely Argonauta.

 

   MONOTHYRA. A term used by Aristotle to designate spiral univalves.

 

   MONOTIGMA. Gray. A genus founded on the species represented fig. 371.

   It is a turrited shell, but we are unacquainted with the characters of

   the genus.

 

   MORIO. Montf. CASSIDARIA, Auct. C. Echinophora, fig. 407.

 

   MOTHER OF PEARL. This beautiful substance, which is so much resorted to

   for ornamental purposes, constitutes the thickened coating of the

   internal surface of the shell named by scientific collectors,

   Meleagrina Margaritifera, commonly called the Pearl Oyster, a young

   specimen of which is figured (164) in our plates. The reason why this

   substance is called mother-of-pearl is that the true pearls are

   produced from its surface. They arise principally from accident or

   disease, and are sometimes artificially produced by pricking through

   the outside of the shell while the animal is living. The animal is

   allowed to live until it has formed a pearl over the wounded part.

 

   MOULINSIA. Grateloup. PUPINA, Vignard. A