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.