Bay of Bengal and the Arabian Sea. Lz 
margo dorsi anticus vix arcuatus, leviter declivis, posticus longior, 
subconcavus, equaliter descendens, ventralis late curvatus ; area 
dorsalis utrinque anguste excayvata, area postica distinctius mar- 
ginata quam antica ;,umbones concentrice fortiter striati, ante- 
mediani ; pagina interna albida; dentes posteriores 20, anteriores 
circiter 18; sinus pallii latus, mediocriter profundus. 
Longit. 12 millim., alt. 74, diam. 6. 
Hab. Station 162, Bay of Bengal, off Coromandel coast, 
145-250 fathoms. 
The transverse plice on the central part of the valves, 
which become obsolete on each side, are very fine and only 
just visible to the naked eye. Like Nuculana lugubris, 
A. Adams, this species has no internal cartilage, the ligament 
being placed on the hinge-line, beneath and on each side of 
the umbones. 
Malletia conspicua. (Pl. II. fig. 12.) 
Testa inwquilateralis, transyersim oblonga, mediocriter convexa, 
subtenuis, antice angustata, postice latior, concentrice tenuiter 
striata, epidermide tenui, nitida, dilute olivacea induta; area 
dorsalis utrinque umbones linearis, excavata, carinis marginata ; 
margo dorsi anticus brevis, rectus, leviter obliquus, posticus fere 
horizontalis, duplo longior ; margo ventralis late arcuatus, utrin- 
que curvate adscendens ; umbones paulo prominentes, approximati, 
in 4 longitudinis siti; linea cardinis mediocriter tenuis, dentibus 
acutis anterioribus circiter 18 et posticis 30 instructa; pagina 
interna nitens, albida, lineam pallii late sed haud profunde sinua- 
tam exhibens; ligamentum parvum, convexum, prominens, oli- 
vaceo-fuscum. 
Longit. 213 millim., alt. 13, diam. 8. 
Hab, Station 177, lat. 18°47! 49" N., long. 73° 7' K., depth 
636 fathoms (Arabian Sea, off west coast of India). 
The valves are very thin and sharp at the ventral and 
lateral margins, and become somewhat thicker and stronger 
towards the umbones. The difficulty of closing the parted 
valves makes it impossible to say to what extent this species 
may gape at the ends; but, so far as I am able to judge, the 
valves would not quite close either in front or behind. ‘he 
striae upon the greater part of the surface are strong and 
regular, but posteriorly as they curve up to the dorsal margin 
they become weaker, so that this part of the valves has a 
slightly smoother appearance. 
M. arrouana, Smith, is an allied species, but of a some- 
what different form, with less regular and not such close 
concentric stria. 
Ann. & Mag. N. Hist. Ser. 6. Vol. xvi. 2 
