4 
17 
thick ligament under the posterior side of the umbo, while 
the left valve has two small diverging cardinal teeth, and a 
small supplementary ridge; no lateral teeth. 
Measurement :— Anterior to posterior, g; umbones to 
margin, 8 ; thickness (valves united), 54 millim. 
Hab. :—Cape Natal, 54 fathoms. 
This shell has much the form of the European P. granulata, 
Nyst, but it is much more closely and conspicuously granulated. 
PoROMYA CURTA, n.sp. (Plate VII., fig. 13). Shell thin, 
ventricose, nearly equilateral, slightly inequivalve, raised at the 
umbones, rounded in front and below, posterior very slightly 
produced and truncated, obtusely angled ; surface iridescent, 
covered with very minute somewhat distant granules which 
are more crowded in front of the posterior angle, forming 
radiating ridges towards the posterior dorsal margin, while 
concentric grooves or growth lines may be seen with a lens. 
Posterior dorsal margin sloping, slightly incurved, anterior 
much sloping, convex; posterior lateral margin obtusely 
biangular, anterior rounded. Umbones nearly central, tumid, 
anteriorly incurved at the apices ; ligament external, narrow. 
Hinge narrow ; cardinal teeth small, two in the left valve and 
one in the right. Interior silvery white. rayed with faint 
irregular striz. 
Measurement :—Anterior to posterior, 9}: umbones to 
ventral margin, 84; thickness (valves united), 7 millim. 
Hab. :—Cape Natal, N. by E., 24 miles; 440 fathoms. 
The shell is unusually short, high and ventricose, otherwise 
it somewhat resembles the European P. gvanulata. 
Fam. Cuspidariide. 
CUSPIDARIA OPTIMA, n.sp. (Plate VII., fig. 16). Shell 
equivalve, inequilateral, thin, white, rounded in front, acumi- 
nated and shortly rostrate behind ; surface obliquely ridged, 
ridges narrow and not very close, excepting near the margin, 
where they become more crowded and concentric. Umbones 
rather depressed, approximating, situated nearer the anterior 
than the posterior end of the shell. Posterior dorsal margin 
strongly incurved, with a concavely depressed area ; anterior 
convexly sloping; ventral margin arcuate, slightly sinuated 
posteriorly ; rostrum rather short, convexly rounded, obtusely 
angular at the sides. Interior silvery white, radiately striated ; 
posterior abductor scar triangular, clearly defined, anterio1 
indistinct ; hinge normal, the process bearing the ligament 
being of moderate size. 
C 
