REPORT ON THE LAMELLIBRANCHIATA. 235 



This species is transversely ovate, sharply rounded in front, produced and acuminate 

 liehind. It is considerably inequilateral, moderately convex, transparent white, glossy 

 near the umbones, finely concentrically striated beneath. The dorsal margins are al)Out 

 equally oblique, the anterior being the least convex, the posterior longer and almost 

 rectilinear, or the least concave after a slight rise near the umbones. The beaks are small, 

 but little raised and glassy. The hinge-plate is fairly strong, and armed with about ten 

 teeth in front of the centre, and thirteen behind. The lunule is not easUy seen, but is 

 very narrow and margined by a slender ridge. The postei'ior area is much larger, well- 

 defined by a ridge radiating from the umbones to the extremity, and has an inner keel 

 on each side nearer the centre enclosing a space only a trifle larger than the lunule. 



Length 4 mm., height 2^, diameter 1^. 



Habitat. — Station 24, off Culebra Island, West Indies, in 390 fathoms ; Pteropod ooze. 



Leda despecta, n. sp. (PL XIX. figs. 8-8a). 



Testa parva, rotunde subovata, intequilateralis, convexa, albida, cencentrice fortiter 

 striata, striis pone medium evanidis. Margo dorsi anticus brevis, leviter declivis, 

 eurvatus, posticus longior, parum obliquus, subrectus. Latus anticum acute rotundatum, 

 posticum latins. Umbones rotundati, obtusi, antemediani. Linea cardinis subvalida, 

 dentibus ad sedecim instructa. 



This little species is peculiar on account of its rounded Pisidium-Yike form, and the 

 rather strong, concentric strife, which become obsolete a little behind the centre of the 

 valves, and very feeble close to the anterior side. It is a little longer than high, rather 

 convex, white, glossy, somewhat inequilateral, narrower and more sharply rounded in 

 front than behind, and prominently curved beneath. The front dorsal margin is short, 

 slightly curving and oblique, the posterior being longer, straighter, and also a little 

 sloping. The beaks are rounded and rather lilunt, and decidedly in front of the centre. 

 The hinge-plate is rather broad, and the teeth, of which about nuie are behind and seven 

 in front of the beaks, are strongish. 



Length 2^ mm., height If, diameter 1. 



Habitat. — Station 24, off Culebra Island, West Indies, in 390 fathoms ; Pteropod ooze. 



This species probably attains a larger size than that of the shells here described. 



Leda lata (Hinds).. 



Niiciila lata, Hinds, Proc. Zool. Soc. Lond., 1843, p. 99. 



Nuada lata, Hinds, Zool. Voy. "Sulphur," p. 64, pi. xviii. fig. 10. 



LMa lata, Hanley, in Sowerby's Thes. Conch., vol. iii p. 116, pi. ccxxvii. figs. 44, 4-5 



Lceda lata, Sowerby, Conch. Icon., vol. xviii. pi. vii. figs. 44, a, h. 



Habitat. — Station 189, Arafura Sea, in 25 fathoms; green mud. 



