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Show 1880.] MR. E. A. SMITH ON THE GENUS MYODORA. 579 right deep or convex. An equal amount of uncertainty prevails respecting the anterior and posterior ends of the shell. Reeve, Woods, and Hanley describe the former as truncated and the latter as rounded. On the other hand, Woodward, Adams, Gould, Philippi, and Hutton, hold a precisely opposite opinion respecting these parts. In this genus it is a constant character that one valve is flatter than the other; and in the description of the following new species the terms "flat valve" and " deep valve " will be employed, thus removing all doubt respecting which valve is spoken of; and the truncated end, or, in other words, that towards which the beaks incline, will be termed the posterior extremity, and the opposite curved end the anterior. Generic Characters of Myodora. Animal unknown. Shell inequivalve; one valve flattish, the other convex ; white, more or less truncated at the posterior extremity, rounded in front, concentrically sulcated. Hinge composed of the sharply reflexed dorsal margins of the flat valve, forming pseudo-lateral teeth, which fit into corresponding elongate grooves in the deep valve. Cardinal teeth none. Ligament internal, situated in a triangular space beneath the umbones, and supported (probably always) by a free shelly structure termed the clavicle. Exterior of valves sculptured with microscopic concentric strise, interrupted by others radiating from the umbones. Interior more or less nacreous, marked with one or more impressed rays curving from the umbones towards the ventral margin. Pallial impression with a small sinus. Genus MYODORA. Myadora, Gray, Ann. Nat. Hist. 1840, p. 306 ; id. Synopsis Brit. Mus. 1840, p. 136. Myodora, Gray, Synopsis, p. 150; id. P.Z.S. 1847, p. 191. Myadora, Reeve, Con. Icon., Monograph; id. P.Z.S. 1844, p. 91 ; Woodward, Man. Moll. p. 499. Myodora, Hanley, Cat. Rec. Bivalve Shells, p. 338; H. & A. Adams, Gen. Rec. Moll. vol. ii. p. 371 ; Conrad, Amer. Journ. Conch, vol. iv. Appendix, p. 71 ; Chenu, Man. de Conch, vol. ii. p. 51 ; Philippi, Handbuch der Conch, u. Malacozool. p. 322. Pandora, Quoy & Gaimard, Voy. Astrolabe, Zool. vol. iii. p. 537 (striata); Sowerby, Appendix to Stutchbury's Sale Cat. p. 3 (brevis). Anatina, Stutchbury, Zool. Journ. vol. v. p. 99, 100 (brevis, pandoriformis, crassa, ovalis). 1. MYODORA STRIATA (Quoy & Gaimard). Pandora striata, Quoy & Gaimard, Voy. Astrolabe, Zool. vol. iii. p. 537, pl. 83. f. 10; Jay, Cat. Shells, ed. 3, p. 120, pl. 6. f. 6, 7. Myadora striata, Gray, MSS., Reeve, Con. Icon. f. 6-6c; id. P.Z.S. 1844, p. 93. Myodora striata, Deshayes, Chenu, Man. de Conch, vol. ii. p. 52, fig. 215. |