Part 17

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._ 1. 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 genus of small land shells with enamelled surface and spiral operculum. See PUPINA.

MOURETIA. Gray. "_Gadin_," Adanson. A genus of patelliform shells, described as differing from SIPHONARIA (the original Mouretia of Adanson) in the situation of the siphon, which in Mouretia is close to the place where the muscular impression is interrupted to leave a space for the head; while in Siphonaria it is nearly half way between the anterior and posterior ends of the shell.

MOUTH. The aperture or opening of univalve shells.

MULINIA. Gray. A genus composed of species of MACTRA, Auct. described as having the ligament (properly so called) internal, and lateral teeth simple. _Ex._ fig. 82. M. bicolor; Mactra, Auct.

MULLERIA. Fer. _Fam._ Ostracea, Lam.--_Descr._ Irregular, subquadrate, inequivalve, inequilateral, foliaceous, attached, pearly within, green, horny without; hinge irregular, with a partly external ligament, passing to the interior, through a sort of sinus.--_Obs._ This remarkable shell resembles Etheria in general form and appearance, but is distinguished by having only one muscular impression. It is so rare that, although not very beautiful, a specimen has been known to produce £20. at a sale. Fig. 192.

MULTILOCULAR. Many chambered.

MULTISPIRAL. (_Multus_, many, _spira_, spire.) A term applied to a shell when the spire consists of numerous whorls; or to an operculum of numerous volutions.

MULTIVALVE. (_Multus_, many; _valva_, valve.) Consisting of numerous valves. There are three kinds of multivalve shells: 1st. Those in which the valves are arranged in pairs, and produce a flattened figure, as Pedunculated Cirripedes, fig. 34 to 43; 2nd. Those in which they are arranged circularly, as Sessile Cirripedes, the valves of which are of two kinds; the _opercular_, consisting of several valves, which close the aperture, and the _parietal_, consisting of those which surround the body of the animal in a circular form, fig. 14 to 33. 3rd. Those in which they are arranged in a straight line, as Chiton, fig. 227.

MUREX. Auct. (_A sharp rock._) _Fam._ Canalifera, Lam. siphonostoma, Bl.--_Descr._ Turrited, ventricose, thick, with three or more longitudinal, continuous, branched, spinose or fringed varices; spire prominent, acute; aperture oval, terminating in a posterior, partly closed canal, outer lip varicose, inner lip smooth, laminar; operculum horny, concentric, pointed.--_Obs._ This genus contains some of the most exquisitely beautiful shells in existence, the richness of their colouring, the ramifications of their varices, would render most species the finest possible subject for the exercise of the painter's art in still life. The most remarkable are the Rosebud Murex, with its pink-tipt fringes, the Venus Comb, with its long rows of parallel spines; the Ducal Murex, the Royal Murex, and many others, which are much sought after by collectors. Murex may be distinguished from Triton by the continuity of the varices, which follow each other in a tortuous direction on the spire. The Ranellæ have only two rows of varices, and have a posterior as well as anterior canal; while Murices have three or more varices, and only one canal. The genus Typhis consists of several small species resembling Murex in every respect, excepting that of having a tubular opening on the upper part of the whorl between each varix. See TYPHIS. The most beautiful Murices are brought from tropical climates. Fig. 395, 396.

MURICANTHUS. Sw. A sub-genus of Murex, thus described: "Varices numerous, foliated; spire short; margin of the outer lip with a prominent tooth near the base; Radix. _Sw._ Zool. Ill. 2nd series. pl. 113, Melanomathus. En. Méth. 418. f. 2." Sw. p. 296. The latter of the two species quoted, however, does not agree with the description, having no prominent tooth on the margin of the outer lip.

MURICATED. (_Muricatus._) Having sharp points or prickles.

MURICIDEA. Sw. A genus of "Muricinæ," Sw. thus described, "Spire more produced, as long or longer than the body whorl; varices numerous; no internal channel at the top of the aperture." Sw. p. 297, and consisting of the following incongruous species, "Lamellosa. Chem. f. 1823, 4. magellanica. En. M. 419. f. 4. peruviana. Ib. f. 5. senticosa, Ib. f. 3. scaber. En. Méth. 419. f. 6. hexagona. Ib. 418. f. 3. erinacea. Mart. f. 1026." Sw. p. 297.

MUSCULAR IMPRESSIONS are the marks or areas formed on the interior surface of shells by the muscular fibres which attach the animals to them. Lamarck has divided his Conchifera into two kinds: 1st. Monomyaria, those which have but one adductor muscle, and consequently have but one impression in each valve, as the common Oyster, fig. 180; 2nd. The Dimyaria, those which have two, and consequently have two impressions in each valve. There are other smaller impressions in some shells besides the principal. The palleal impression is a mark or scar passing near the margin of the shell. See Introduction.

MYA. Auct. _Fam._ Myaria, Lam. Pyloridea, Bl.--_Descr._ Transverse, oval, thick, gaping at both extremities, rounded anteriorly, acuminated posteriorly; hinge with one large, dilate, compressed tooth in one valve, and a suture in the other, containing the cartilage; muscular impressions two, distant, large, irregular; palleal impression with a large sinus.--_Obs._ Mya may be known by the large, prominent, broad tooth in one valve. In Anatina there is one in each valve, and, in Lyonsia, accessory pieces. Lutraria has cardinal teeth and a ligamentary pit. Few species of Mya are known. They belong to the Northern Hemisphere. M. truncata, fig. 71.

MYCETOPODA or MYCETOPUS. D'Orb. _Fam._ Nayades, Lam.--_Descr._ Shell elongated, soleniform, inequivalve, inequilateral, gaping anteriorly; muscular impressions very complex.--_Obs._ These shells are said to terebrate like Pholas. Fig. 151. M. solenoides.

MYARIA. Lam. A family belonging to Lamarck's order Conchifera Dimyaria. Containing the following genera:

1. ANATINA. Ligament in a spoon-shaped prominence on the hinge of each valve, shell thin. Fig. 69.

2. MYA. Spoon-shaped prominence in one valve; shell thick. Fig. 71.

3. ANATINELLA. A spoon-shaped process in both valves. Fig. 70.

4. LYONSIA. An internal bony appendage on the hinge. Fig. 491, 492.

5. MYOCHAMA. Flat valve attached, a bony appendage on the hinge. Fig. 73.

6. CLEIDOTHÆRUS. Deep valve attached, a bony appendage. Fig. 75, 76.

7. CUMINGIA. Ligamentary pit in both valves, spoon-shaped. Fig. 87.

MYOCHAMA. Stutch. (_Mya_ and _Chama_.) _Fam._ Myaria, Lam.--_Descr._ Inequivalve, irregular, attached, subequilateral; attached valve flat, with two marginal, diverging teeth, and one end of a little testaceous appendage fixed between them by a horny cartilage; free valve convex, with umbo incurved and two very minute, diverging teeth, between which the other end of the testaceous appendage is placed; external surface of both valves conforming to the grooves or undulations of the shell to which the specimen is attached; muscular impressions two in each valve; palleal impressions with a short sinus.--_Obs._ This new genus, of which only one species is known, the M. anomioides from New South Wales, differs from Anomia and Anatina in being attached by the surface of one of the valves, from which circumstance the word Chama is added to its name; the little testaceous appendage bringing it near the Myariæ. Fig. 73, M. anomioides.

MYOCONCHA. Sow. (_Mya_ and _Concha_.) _Fam._ Cardiacea, Lam.--_Descr._ Oval, equivalve, oblique; umbones terminal; ventral margin rounded; hinge with an external ligament, and one oblique, elongated tooth in the left valve; impression of the mantle not sinuated.--_Obs._ The fossil genus has the general form of Mytilus or Modiola, but the hinge of the Conchæ generally.

MYOPARA. Lea. (_Myoparo_, a piratical oar-galley.) _Fam._ Arcacea, Lam. A genus founded on a minute fossil bivalve shell, somewhat resembling Isocardia in form, but having a series of teeth placed on each side of the umbones. M. costatus, fig. 135.

MYRISTICA. Sw. A genus of "Pyrulinæ," Sw. thus described: "Sub-pyriform; spire strong, spiny, or tuberculated, nearly as long as the base; umbilicus either partially or entirely concealed; inner lip vitreous, thin; the outer with an internal and ascending canal; the basal channel wide. Hippocastanea. En. M. 432. f. 4. lineata, Ib. f. 5. melongena. En. Méth. 435. f. 3. nodosa. Chem. 1564. 5." Sw. p. 307. _Ex._ P. Melongena, Fig.

MYRTEA. Turt. VENUS spinifera, Auct. LUCINA spinifera, Nonnull. The shells of this genus are described as "Oval, triangular, equivalve, nearly equilateral, closed. Hinge of one valve with a single tooth, and lateral one on each side; of the other valve with two teeth, the lateral ones obscure. Ligament external." British Channel and Mediterranean.

MYSCA. Turt. A genus composed of species of UNIO, Auct. which are distinguished by having "strong, transverse, notched, cardinal and long lateral teeth." Unio pictorum.

MYSIA. Leach. A genus composed of TELLINA rotundata, montagu and other similar species.

MYTILACEA. Bl. The fourth family of Lamellibranchiata, Bl. The shells are described as regular, equivalve, frequently with a thick, horny epidermis. A toothless hinge and a linear ligament. This family contains the genera Mytilus and Pinna.

MYTILACEA. Lam. A family belonging to the first section of Conchifera Monomyaria, Lam. described as having the ligament partly interior, occupying the greater part of the hinge line, which is straight. The shell is rarely foliaceous. The Mytilaceæ cannot easily be confounded with the Malleaceæ, because the former are generally regular and the latter are irregular, and have a thick internal coating of pearl, beyond which the external coating extends. The genera may be thus distinguished:

1. MYTILUS. Umbones terminating in a point. Fig. 158.

2. DREISSINA. The same, with a septiform plate. Fig. 159.

3. MODIOLA. Anterior margin rounded beyond the umbones. Fig. 160.

4. PINNA. Open at the posterior extremity. Fig. 162.

5. LITHODOMUS. Cylindrical, living in holes. Fig. 161.

MYTILUS. Auct. _Fam._ Mytilacea. Lam.--_Descr._ Equivalve, cuneiform, oblique, smooth, with umbones terminal, pointed, and posterior side broad, rounded; hinge linear, with a long, partly internal ligament; muscular impressions two in each valve, that on the posterior side large, irregular; that on the anterior small; palleal impression irregular.--_Obs._ The Linnean genus Mytilus included the Modiolæ, which differ from the Mytili in the rounded anterior side; and the Pinnæ, which are large shells, gaping at the posterior extremity. M. achatinus, fig. 158.

NÆARA. Gray. A genus composed of ANATINA longirostrum, Lam. and other similar species.

NAIA. Sw. A sub-genus of Castalia, Lam. thus described: "Oval, cardinal teeth beneath the bosses, and deeply sulcated, C. corrugata. _Lam._ En. Méth. 248. f. 8, picta. _Sw._ En. Méth. 248. f. 6." Sw. p. 379.

NANINIA. Gray. A genus composed of the planorbicular species of HELIX, with large umbilici, and outer lip thin, included in the sub-genus Helicella, Fer. _Ex._ H. citrina, fig. 280.

NASSA. Lam. A genus of small shells united to Buccinum by some authors, but separated by others on account of the little tooth-like projection terminating the columella. N. arcularia, fig. 423.

NATICA. Brug. _Fam._ Neritacea, Lam. Hemicyclostomata, Bl.--_Descr._ Globose, thick, generally smooth; spire short, pointed, with few volutions; aperture semilunar, entire; outer lip thin; columellar lip oblique, nearly straight, callous; umbilicus with a spiral callosity, terminating behind the columella, and sometimes filling up the cavity; operculum shelly in some species, horny in others; epidermis thin, light, semitransparent.--_Obs._ The straight, callous, smooth edge of the columella and the callosity serve to distinguish this genus from Nerita, Neritina, Neritopsis and Helix. Fig. 327, 328.

NATICARIA. Sw. A sub-genus of Natica, thus described: "Oval; convex above; umbilicus small, open, placed very near the top of the aperture; inner lip reflected; small. N. melanostoma, Mart. 189. f. 1926, 1927. cancellata, _Sw._ Ib. 189. f. 1939. bifasciata, Griff. Cuv. 1. f. 2." Sw. p. 346.

NATICELLA. Guild. A sub-genus of Natica, thus described: "Operculum horny; shell globose, but generally depressed; umbilicus nearly filled up by a vitreous deposition of the inner lip; spire obtuse. N. aurantia. Mart. 189. f. 1934, 1935." Sw. p. 345.

NAVICELLA. Lam. (_A little ship._) _Fam._ Neritacea, Lam. Hemicyclostomata, Bl.--_Descr._ Transversely oval, symmetrical, smooth; aperture entire, oval; dorsal surface convex; outer lip thin; inner lip flat, straight edged; spread over the front surface of the body whorl, and sometimes hiding the apex; apex incurved; operculum testaceous, flat, sub-quadrate, with a lateral articulation.--_Obs_. This well known genus, of which there are several species, is named Cimber by Montfort. The shells are brought from India, the Isle of France and the Moluccas. Fig. 323, N. elliptica.

NAUTELLIPSITES. Parkinson. A generic name proposed to include such species of Nautilus as have been compressed, so as to assume an oval instead of a round form. The genus Ellipsolites of De Montfort consists of species of Ammonites similarly deformed.

NAUTILACEA. Bl. The fifth family of Polythalamacea, Bl. the shells of which are described as more or less discoidal, compressed, symmetrically convolute; the last whorl much longer than the others; which are entirely hidden beneath it and advancing beyond the last but one, so as constantly to form a large oval aperture, which is always, however, modified by the last whorl. The septa are united in the greater number of instances and pierced by one or more (?) siphons. This family contains the genera Orbulites, Nautilus, Polystomella and Lenticulina.

NAUTILACEA. Lam. The sixth family of Polythalamous Cephalopoda, Lam. containing the genera Discorbites, Siderolites, Polystomella, Vorticialis, Nummulites, Nautilus. To these may be added Simplegas and Endosiphonites. Fig. 472 to 476.

NAUTILUS. Auct. (_A little boat._) _Fam._ Nautilacea, Lam. and Bl.--_Descr._ Convolute, discoid, chambered, symmetrical; spire partly or entirely concealed by the last whorl; aperture modified by the last whorl, wide, sinuated on the dorsal margin; interior surface pearly; septa dividing the chambers simple; siphon discontinuous.--_Obs._ The shell named Nautilus by Pliny is the Argonauta of modern authors, a thin shell, not chambered. The Nautili are known from the Ammonites by the septa being simple, not sinuated as in the latter genus, and in general the volutions of the spire are not visible. Three or four species are known inhabitants of the Pacific Ocean and Australian Ocean. The fossil species are found in the tertiary, and also in the secondary strata, as low down as the Mountain limestone. N. pompilius, Frontispiece.

NAYADES. Lam. A family of the order Conchifera Dimyaria, Lam. described as containing fresh-water bivalve shells, with or without teeth on the hinge. They are all pearly within, and have a thick, rather smooth epidermis without. This family contains a great variety of shells, which have been separated into an immense number of genera, but which G. B. Sowerby, sen. gives very good reasons for uniting under one generic name. The most generally received distinctions are as follows:

1. CASTALIA. Two cardinal, one lateral, ribbed teeth. This genus is removed from the family of Trigonacea. Fig. 140.

2. UNIO. Teeth various. Fig. 142, 145, 149, 148, 147, 151, 141.

3. HYRIA. Trigonal, alated. Fig. 143, 150.

4. ANODON. No teeth. Fig. 152.

5. IRIDINA. Hinge crenated. Fig. 150.

NECTOPODA. Bl. The first family Nucleobranchiata, Bl. containing the genera Carinaria and Firola; the latter is not a shell.

NEMATOPODA. Bl. The first class of the sub-type Malentozoa, Bl. containing all the mollusca with multivalve shells, except Chiton, and divided into the families Lepadicea and Balanidea, corresponding with Lamarck's sessile and pedunculated Cirripedes, and with the Linnæan genus Lepas.

NEMATURA. Benson. _Fam._ Turbinacea, Lam.--_Descr._ Thin, nearly oval, somewhat compressed from back to front; spire acute, consisting of few rounded whorls; last whorl large, but contracted near the aperture; aperture small, oblique, rounded anteriorly; peritreme continuous, thin; operculum spiral, horny, with few volutions.--_Obs._ The distinguishing character of this genus is the contraction of the last whorl near the aperture, in which respect it is nearly resembled by the shell called Cyclostoma lucidum. Two recent and one fossil species, all very minute, are described by Sowerby in Loudon's Magazine of Natural History, New Series. Fig. 305.

NERINEA. Defr. _Fam._ Canalifera, Lam.--_Descr._ Turrited, oblong, sub-canaliculated, consisting of numerous whorls; aperture with a strong fold on the columella, one on the outer lip, and one on the inner lip at the edge of the body whorl.--_Obs._ This genus is only found in a fossil state usually in the Oolitic beds, it is not resembled by any other; the strong, prominent folds on the three upper angles of the subquadrate aperture present a singular appearance in a section. One species has been named N. Hieroglyphus. We give N. Goodhallii, fig. 374.

NERITA. Auct. _Fam._ Neritacea, Lam. Hemicyclostomata, Bl.--_Descr._ Smooth or ribbed, semiglobose; spire short, sometimes flat, consisting of few volutions; aperture large, semilunar; outer lip thick, entire; inner lip thickened, dentated at the edge, spread over the body whorl, forming a flattened disc; operculum shelly, spiral, with an appendage by which it is locked under the sharp edge of the columella.--_Obs._ These marine shells are known from Neritina by the thickness of the shell and the want of the thick, horny, dark coloured epidermis; from Natica by the flat area produced by the spreading of the thickened columellar lip. N. Peloronta, fig. 330. N. polita, fig. 329.

NERITACEA. Lam. A family of the first order of Trachelipoda, Lam. containing the following genera:

1. NAVICELLA. Apex terminal, not spiral; inner lip septiform. Fig. 323.

2. NERITA. Columellar lip septiform, edge with distinct teeth; shell thick. Fig. 330.

3. NERITINA. Shell thin; columellar lip septiform, edge denticulated; generally a thick, dark coloured epidermis. Fig. 324 to 326.

4. NATICA. Having an umbilicus behind the columellar lip, with a spiral callosity. Fig. 327, 328.

5. NERITOPSIS. Edge of the columellar lip with a deep notch. Fig. 331.

6. PILEOLUS. Patelliform; apex central; columellar lip septiform, leaving the aperture small. Fig. 332.

7. JANTHINA. Columellar lip linear; aperture angulated. Fig. 333.

NERITINA. Lam. _Fam._ Neritacea, Lam.--_Descr._ Thin, semiglobose, obliquely oval, smooth, flattish in front; spire short, sometimes depressed, consisting of few rapidly increasing whorls; aperture semicircular; outer lip thin, sharp; columellar lip broad, flat, its inner edge straight, denticulated; operculum testaceous, semicircular, sub-spiral, with an articulating process on the inner edge.--_Obs._ This genus of fresh-water shells differs from Nerita in the minuteness of the denticulation of the columella, as well as in the characters mentioned in our observations upon the latter genus. N. spinosa, (Clithon, Montf.) fig. 325. N. virginea, fig. 324. N. perversa, Lam. (Velates, Montf.) fig. 326. All the species known up to the present time, with the exception of three, are represented in the author's Conchological Illustrations, parts 86, 87, 90, 91, 94 to 100. The catalogue accompanying these representations enumerates 59 species.