246 THE VOYAGE OF H.M.S. CHALLENGER. 



Several Stations iu the Atlantic have already been recorded by the late Dr. Gwyu 

 Jeffreys for this species. 



Malletia pallida, u. sp. (PI. XX. figs. 8-8a). 



Testa convexiuscula, insequilateralis, augusta, elongata, anticc acute rotundata, 

 postice angustior, subacuminata, uitida, albido-flavescens, incrementi lineis tenuibus 

 striata, lineis paucis albidis radiantibus ornata. INIargo dorsi anticus leviter declivi.=s, 

 parum arcuatus, posticus longior, rectilinearis, vix obliquus. Margo inferior late 

 curvatus, postice indistincte sinuatus. Umbones parum prominentes, haud acuti, 

 involuti. Ligamentum elongatum, gracile, vix prominens, pone umbones carina 

 gracillima utriuque marginatum. Linca cardinis angusta, dentilnis ad 36 instructa. 

 Pagina interna alba. 



This species is thin, inequilateral, moderately convex, very glossy, white, and 

 clothed wdth a very thin pale yellow epidermis. It is long, sharply rounded at the 

 anterior end, narrowed and bluntly acuminate behind. The sculpture consists of very 

 fine lines of growth and a few coarser striae near the lower margin at the central part 

 of the valves, and at the posterior end there are two faint radiating white lines and a 

 few others still less noticeable upon the rest of the surface. The front dorsal margin is 

 a little convex and oblique, the posterior being considerably longer, rectilinear, and 

 about equally inclined. The ventral outline is regularly broadly curved, and exhibits 

 only the faintest indication of a posterior emargination. The umbones are small, 

 incurved at the tips, a little raised above the dorsal line, and situated at about three- 

 eighths of the total length from the anterior end. The ligament is small, narrow, and 

 bordered on each side by the raised keel-like posterior edge of the valves. In front of 

 the beaks there is also a slight ligament or thickening of the epidermis which connects 

 the valves. The hinge-plate is moderately slender, and furnished with about thirty-six 

 denticles, of which about twelve are anterior to the centre. The interior is white, and 

 exhibits only a shallow sinus in the pallial impression. 



Length 16^ mm., height 9^, diameter 6. 



Habitat. — Station 137, Mid South Atlantic, between Tristan da Cunha and the 

 Cape of Good Hope, in 2550 fathoms ; red clay. 



Malletia veneriformis, n. sp. (PI. XX. figs. 9— 9a). 



Testa ovata, convexa, paulo insequilateralis, alba, nitida, concentrice tenuiter lirata 

 et sulcata. Umbones prominentes, iucurvati, antice versi. Dentes numerosi, utriuque 

 elongati, acuti, in medio umbones infra minuti, haud interrupts Ligamentum 

 marginale, angustum, in suico supra dentes parvos, infra umbones situm. 



