16 
sight P. hyalina, Sowerby, which has been found in the 
China Sea, but it differs considerably both in form and sculp- 
ture from that species. 
PoOROMYA STRIATA, n. sp. (Plate VII., fig. 11). Shell trans- 
versely sub-ovate, inequilateral, rather inflated, of a thin 
nacrous. substance, covered by a thin light buff scabrous. 
epidermis ; posterior side obtusely biangular, anterior rounded ; 
surface very finely and closely granular, rayed with numerous. 
very thin thread-like ridges. Posterior dorsal margin rather 
short, obtusely angled, nearly straight, slightly sloping ; 
anterior slopingly convex; posterior lateral margin nearly 
vertical, anterior rounded ; ventral margin arcuate. Umbones. 
prominent, approximating, incurved, inclined anteriorly, situa- 
ted rather nearer the posterior than the anterior side of the shell. 
Ligament small, immersed, very narrowly produced posteriorly. 
Interior silvery white. Hinge of moderate thickness; right 
valve with one prominent cardinal tooth, with a slightly 
curved cusp at the top, and a blunt point on each side ; left 
valve with two small parallel teeth. 
Measurement :—Anterior to posterior, 22; umbones to 
ventral margin, 164; thickness (valves united), 11} millim. 
Hab. :—Vasco de Gama Pk. (False Bay), S. 75° E., 134 miles ; 
166 fathoms. 
This shell differs-from P. Gilchristi, in being less regularly 
oval in form, rather more compressed, and in the character of 
the surface, which is covered with thin raised radiating strie, 
POROMYA GRANOSISSIMA, n. sp. (Plate VII., fig. 12). Shell 
nearly equilateral, rather short, angularly acuminated above, 
rounded in front and below, posterior truncated with an obtuse 
but distinct angle from the umbones to the margin ; surface 
very profusely and distinctly granular all over; granules. 
minute, rounded, very close together, arranged so as to form 
fine close radiating ridges, where removed the surface of the 
shell is smooth. Posterior dorsal margin almost straightly 
sloping; anterior convex, much sloping; posterior lateral 
margin conyexly vertical, obtusely biangular; anterior and 
ventral margins rounded. The area behind the posterior 
angle is flattened, or very slightly concave. Umbones promi- 
nent, nearly central, approximating, incurved, with a very 
slight anterior tendency at the apices. Cardinal area 
narrow, rather concave, bordered by an angular ridge on the 
right valve, and an extremely thin long and narrow ligament 
on the inner edge of the left. Interior silvery white ; hinge 
of moderate thickness, with a thick prominent cardinal tooth 
in the right valve, and an oblique pit bearing a short rather 
