358 MOLLUSCA. 
mixed with white; surface with about fifteen, unequal, somewhat 
curved, triangular ribs, with fine, intervening striz. Aperture ovate, 
edge very irregularly and profoundly dentate by the prolongation of 
the ribs, especially those over the siphonal canal. Cavity small and 
shallow, the left margin rendered abrupt by a very thick callus over 
the muscular impression, either yellowish or mottled with brown; 
muscular cicatrix very strongly marked; siphonal canal deep, very 
oblique; marginal limb broad, flattened, white or pencilled with 
brown. 
Length one inch; breadth four-fifths of an inch; height one-fifth of 
an inch. 
Inhabits the Sooloo Sea, Mangsi. C. Pickering. 
This flattened, unsymmetrical shell, has a very small, shallow 
cavity, limited to the muscular impression and included space, which 
at one side is straight, abrupt, and excavated, while on the siphonal 
side it is rounded, gently sloping, and effuse, so that the shell looks 
much like the valve of an oyster. The rest of the under surface pre- 
sents a broad, flattened margin. It is allied to S. atra, to which it 
may possibly be traced by its varieties; but it is more elongated, less 
symmetrical, and the ribs, which are much more numerous on the left 
than on the right side, surpass the margin to a much greater extent. 
Figures 467, 467 a, 467, outer, inner, and profile views of the 
shell. 
SIPHONARIA INCULTA (Gould). 
Testa parva, crassa, trregularis, depresso-conica, costulis vigintt ad 
viginti-quatuor radiata ; apice sub-centrali: cavositas profunda, latere 
sinistro precipit, latere dextro declivi; fundo fusco-nubeculato ; cica- 
trice muscular profunda ; limbo marginal expanso, sericeo, hepatico ; 
margine costulis dentato. 
Stphonaria inculta, Gou.p ; Proceed. Boston Soc. Nat. Hist., i1. 153. 
August 1846. Expedition Shells, 11. 
