15 
acuminated, and slightly flexuose. Posterior dorsal margin 
almost straightly sloping, slightly concave near the umbones ; 
anterior longer, rather convex ; posterior lateral margin nearly 
vertical, obtusely angled above and below ; anterior rounded ; 
ventral margin longer, rather oblique, very slightly convex. 
Umbones small, slightly inclined towards the posterior side ; 
cardinal area very narrow; ligament short. Interior white ; 
hinge line very narrow, with small cardinal teeth ; no lateral 
teeth, but in the left valve the narrow posterior lamina termi- 
nating abruptly gives almost the appearance of one. 
Measurement :—Anterior to posterior, 32}; umbones to 
ventral margin, 20; thickness, 10 millim. 
Hab. :—Tugela River Mouth, N. by W., 27 fathoms. 
ERVILIA PURPUREA ? (DESHAYES). 
Buffalo River (two miles above the jetty). 
I name this with some doubt, the shells being more fragile 
than the typical form from the Red Sea. It may prove to 
be a distinct species. 
Fam. Anatinide. 
Poromya GILCHRISTI, n.sp. (Plate VII., fig. 10). Shell 
transversely oval, nearly equilateral, rather inflated, whitish, 
of a thin nacrous substance, with a very thin light yellowish- 
brown slightly scabrous epidermis about the margin ; surface 
minutely punctured throughout, concentrically very finely 
and inconspicuously striated, and with very slight radiating 
ridges towards the posterior side. Dorsal margin slightly 
sloping on both sides, posterior very obtusely angled, anterior 
convex, rounded ; ventral margin somewhat obliquely arched. 
Umbones prominent, approximating, incurved, slightly inclined 
anteriorly, nearly central; cardinal area slightly impressed, 
rather long and narrow, with a small subulate ligament. 
Interior silvery white; abductor scars irregular in form, 
rugose ; pallial line rather broad, without sinus. Hinge with 
one somewhat prominent, mucronate cardinal tooth in the 
right valve, and two narrow diverging teeth in the left. 
Measurement :—Anterior to posterior, 254; umbones to 
ventral margin, 18}; thickness (valves united), 13 millim. 
Hab. :—Umtwalumi River Mouth, N. by W., seven miles ; 
50 fathoms. 
Only one specimen of this fine species has been found. All 
the species of this genus appear to be extremely rare, and this 
applies to all those described in this paper, as well as those 
previously known. P. Gilchristi somewhat resembles at first 

