MOLLUSCA. 1 1 I 



particularly conspicuous at the pallial line, where they terminate. 

 The muscular scars are large, well defined by a line radiating from the 

 umbones. Hinge-teeth rather numerous, minute in the centre, 

 considerably larger at both ends. In the type there are forty, and 

 a specimen about half-grown has thirty-five. The ligament is 

 narrow, but very coarsely striated transversely. The epidermis is 

 thinnish and somewhat fibrous near the margins, especially pos- 

 teriorly. 



59. Area (Barbatia) symmetrica. 



Area symmetrica, Reeve, Conch. Icon. st>. 117, and fig. 120. 

 PVar.=Arca zebueusis, Reeve, I.e. fig. 117, sp. 120. 



Hub. Port Molle, Queensland, 12-20 fms. (Coppinger) ; Bay of 

 Manila {Cuming). 



In the ' Conchologia Iconica' the numbers of the figures 120 

 and 117 should be reversed. The specimens of A. symmetrica 

 which were described by Keeve are of a greenish tint, and not so 

 oblique as A. zebiu nsis: The sculpture in both consists of fine 

 radiating lira?, rendered minutely granular by the concentric lines 

 of growth. The lira? vary but little in thickness, with the excep- 

 tion of a few finer intermediate ones here and there and those on 

 the posterior extremity, which are a trifle stouter. A. zebuensis 

 ditiers, in addition to its extra obliquity before referred to, resulting 

 from the less central position of the umbones, in being a trifle more 

 finely lirate. One of the specimens from Port Molle is somewhat 

 intermediate in form, being more oblique than A. symmetrica and 

 less so than A. zebuensis. The measurements of two specimens will 

 indicate to what extent the form and proportions may vary : — 



No. 1. Height 7§ millim., length 11, diameter 8. 



No. 2. „ 6^ „ „ 11, „ 6|. 



60. Area (Trisis) tortuosa. 

 Area tortuosa, Linn. 



Hob. Singapore and Malacca (Cuming); Xorth-west Australia 

 (Du Boulay) and China (Reeves), in Brit. Mus. ; Port Curtis in 

 11 fms., sand and shell bottom (Copjpinger). 



The right valve of this well-known and remarkable shell always 

 appears to retain more of the epidermis than the left. The foot and 

 mouth of the animal, as might be expected, are at the narrow end 

 of the shell. The foot (in spirit) is small, narrow, and grooved 

 beneath, retaining a small byssus. 



61. Leda darwini. (Plate VII. figs. L-L2.) 



Shell a little inequilateral, rather convex, transversely irregularly 

 ovate, acuminate posteriorly, thinnish, glossy, moderately coarsely 

 concentrically ridged and sulcate throughout, except upon the lunule 

 and area, the ridges being finer and the sulci broader on a slightly 

 depressed portion of the surface down the posterior side, which is of 



