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



another, and have a posterior inclination. The hinge-plate is moderately strong, and 

 furnished with al)out twenty-one teeth, of which about nine are in front of the small deep 

 ligamental pit and twelve hehinu it. The interior is glossy, and the scars and pallial 

 impression are not clear. 



Length 3 mm., height 2, diameter l^. 



Habitat. — Station 122, off Pernambuco, Brazil, in 350 fathoms; red mud. 



Although so small, the shells here described appear to be adult. They are devoid 

 of an)^ special striking feature, but are peculiarly contracted and beaked at the 

 posterior end. 



Leda excisa (Philippi). 



Nuciiln excisa, Philippi, Enum. Moll. Sieil., vol. ii. p. 46, pi. .\.v'. fig. 4. 



Malletia excisa, Jeffreys, Proc. Zool. Soc. Lend., 1879, p. 586.^ 



Mallet ia excisa, Jeffre3s, Ann. and Mag. Nat. Hist., 1876, vol. xviii. p. 435. 



Habitat. — Station 70, west of the Azores, in 1675 fathoms; Globigerina ooze. 



The sinus in the posterior side is not quite so marked in the two valves from this 

 Station as in Philippi's figure. 



Althongh stated to be wholly external by Jeffreys, I am of opinion that the valves 

 are also connected by an internal cartilage, because I find a minute pit for its reception 

 as in other species of Leda immediately under the apex of the umbones, and consequently 

 have placed it in that genus. 



Leda decipiens, n. sji. (PI. XIX. figs. 3-3a). 



Testa convexa, insequilateralis, oblonga, antice angusta, acute rotundata, postice 

 insigniter dilatata, qnadrate oblique truncata et concave impressa, liris tenuibus numerosis 

 regularibus oruata. Margo dorsi anticns leviter declivis, fere rectus, posticus longior, 

 horizontalis, rectilinearis aut vix incurvatus. Margo ventris late arcuatus, antice lente 

 adscendens, post medium maxime prominens. Umbones parvi, antemediani, Iseves. 

 Linea cardinalis subcrassa, lata, dentibus circiter trigiuta instructa. Lunula angusta, 

 paulo impressa. Area posterior latior, profunda, acute marginata. 



Length 10 mm., height 7, diameter 5i. 



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



The .slight broad depression down the posterior side causes the fine concentric lirse to 

 be the least flexuose at that part, and the truncation consequently is not absolutely 

 rectilinear. Of the thirty teeth about seventeen are posterior and thirteen anterior. 

 The muscular scars and pallial line are not sufficiently clear for description. 



