586 MR. E. A. SMITH ON THE GENUS MYODORA. [NoV. 16, 



curved on the anterior dorsal margin, and the pallial sinus is much 

 less deep. 



The microscopic radiating striae on the present species are very 

 conspicuous. 



19. Myodora PROXiMA, sp. nov. (Plate LIII. figs. 8, 8a, 86.) 

 M. triangularis, A. Ad. MS. in Mus. Cuming. 



Shell suhequilateral, triangular, thick ; dorsal lines converging to 

 a sharp point, anterior a little convexly curved, posterior a trifle 

 concave near the umbones ; anterior and hinder ends rather sharply 

 rounded, subangular, the latter sometimes more or less obliquely 

 truncated ; ventral margin broadly arcuate. Deep valve not very 

 convex, with only a trace of a depression down the posterior side, 

 rather coarsely lirated from margin to margin ; upper valve flat or 

 very slightly convex, sulcated very nearly as coarsely as the other 

 valve. A single impressed ray in the interior, curving from near 

 the umbones to the inner or lateral boundary of the small paUial 

 sinus in the flat valve, and nearer the centre in the deep one. 

 Posterior scar subrotund ; anterior one more elongate, subpyriforni. 



Length 10 millims., width 10|, diani. 3. 



Hub. Japan, 22-47 fathoms {Capt. H. C. St. John, R.N.) ; China 

 (^Mus. Cuming^. 



This species approximates very closely to M. trigona from the 

 Philippine Islands. It may, however, be specifically separated on 

 account of the more acute ajiical angle, its greater depth from the 

 umbo to the ventral margin, the less-distinct posterior depression 

 on the convex valve, the slighter truncation of hinder margin, and 

 the less regularity and less elevation of the concentric ridges. 



20. Myodora reeveana, sp. nov. (Plate LIII. figs. 10, 10a.) 

 M. reeveana, A. Adams, MS. in Mus. Cuming. 



Shell transversely ovate, posteriorly broadly truncated, anteriorly 

 rounded, suhequilateral ; front dorsal slope of deep valve nearly 

 rectilinear, only feebly arcuate, hinder rather incurved ; concentric 

 ridges very fine, continuous from margin to margin ; upper valve 

 flat, viith a slight depression down the posterior side, finely con- 

 centrically striated. Internal impressed ray a little curved, extending 

 to the inner side of the paUial sinus. 



Length b\ millims., width 7g, diam. 2. 



Hub. China. 



This species is remarkable for the fine concentric sculpture, in 

 which respect it differs from its congeners. M, convexa is lirated 

 nearly as finely, but diff'ers in form. Young specimens of J/, paw- 

 doriformis would probably agree very fairly in the latter character; 

 hut their concentric lirae are much too remote. 



The truncation at the posterior end is very abrupt in this species, 

 and forms almost a right angle with the hinder dorsal slope. The 

 microscopic sculpture is excessively fine in comparison with that of 

 other species. 



