1880.] MR. E. A. SMITH ON THE GENUS MYODORA. 579 



right deep or convex. An equal amount of uncertainty prevails re- 

 specting 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 era|)loyed, thus 

 removing all doubt respecting which vah-e is spoken of; and the 

 truncated end, or, in other words, that towards which the beaks in- 

 cline, will be termed the posterior extremity, and the opposite curved 

 end the anterior. 



Generic Characters q/Myodora. 



Animal unknown. Shell inequi valve; 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 striae, 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. 13G. 



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 ; II. & 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 (hrevis, 

 p and or if or mis, crassa, ova f is). 



1. Myodora striata (Quoy & Gaimard). 



Pandora striata, Quoy & Gaimard, Voy. Astrolabe, Zool. vol. iii. 

 p. 537, pi. 83. f. 10; Jay, Cat. Shells, ed. 3, p. 120, pi. 6. f. G, 7. 



Myadora striata. Gray, MSS., Reeve, Con. Icon. f. Q-Qc ; id. 

 P. Z. S. 1844, p. 93. 



Myodora striata, Deshayes, Chenu, Man. de Conch, vol. ii. 

 p. 52, fig. 215. 



