432 Dr. J. Gwyn Jeffreys on 



pearl-white under the ejjidermiSj which is pale yellowish : 

 vmrqins .sloping on the back towards each side, which is 

 equally rounded (the posterior side being upturned and occa- 

 sionally more or less angular towards the point), semicircular 

 in front : heaks placed about two-fifths nearer the anterior 

 side, very small and incurved : lunule lance-shaped, narrow, 

 and defined by a sharp ridge in the middle : ligament ex- 

 tremely slight : cartilage and pit very small : hinge-line ob- 

 tusely angular, occupying the greater part of the dorsal area : 

 Jiinge-plate narrow : teeth recurved, placed on the inside of the 

 hinge-plate, 7 to 10 on each side : inside glossy ; margin 

 plain : scars slight and inconspicuous. L. 0'175. B. 0*2. 



Station 9, 1750 fms. ; 12, 1450 fms. ; 13, 690 fms. ; 16, 

 1785 fms. One living specimen and some valves. * Por- 

 cupine ' Exp., 1869, off the north-western coast of Ireland, 

 1G5-144.3 fms. ; 1870, ofl:' the coast of Portugal, 740-1095 

 fms. ' Challenger' Exp., lat. 37° 26' N., long. 25° 14' W., 

 1000 fms. 



This has a peculiarly oblique outline, in consequence of the 

 posterior side being upturned ; and the true length (measured 

 from the beak to the front margin) is proportionally greater 

 than in the allied species. Tlie position of the beak is excen- 

 tric compared with that in L. expansa. 



Leda sericea*^ Jeffr. 



Shell transversely oval, somewhat inequilateral, convex, 

 rather solid, opaque, and of a dullish hue : sculpture^ numerous 

 fine, regular, and close-set concentric stride, besides a few occa- 

 sional lines of growth : colour white under the epidermis^ which 

 is pale yellowish : margins sloping from the beak to each 

 side, which is equally rounded, gently curved in front : heaks 

 placed nearer the anterior side, blunt or depressed: lunule 

 long, inconspicuous : ligament slight : cartilage and pit small, 

 the former horn-colour : hinge-line obtuse-angled : hinge-plate 

 rather broad : teeth recurved towards the beak, 7 to 10 on the 

 anterior and 10 to 15 on the posterior side ; those close to the 

 beak are minute and crowded, the others becoming much larger 

 as they diverge outwards : inside smooth ; margin plain : mus- 

 cular scars pear-shaped: ijallial scar distinct, placed within 

 the margin. L. O'l. B. 0-15. 



Var. ovata. Longer in proportion to the breadth. 



Station 12, 1450 fms. ' Porcupine ' Exp., 1869, off the 

 north-western coast of Ireland, 1366-1380 fms. ; 1870, off 

 the coast of Portugal, 740-1095 fms. 



* Silkv. 



