92 KELLIADA. 
in a piece of hollowed-out sandstone rock, it will produce 
another : of these facts we speak with certainty. This species, 
when imbedded in the crevices of rocks, is more globular and 
of firmer texture than those which are found in the muddy 
deposits of old bivalves, taken in the coralline districts, six 
miles from the shore; these are very thin and almost mem- 
branous at the umbones, of larger size and subtriangular 
figure, and have the tube marked with flake-white longitudinal 
lines that are not apparent im the thicker varieties. 
Having examined many of both these variations, without 
detecting a difference in the organs, we must consider them as 
dependent on habitat. 
K. ruspra, Montagu. 
K. rubra, Brit. Moll. i. p. 94, pl. 36. f. 5, 6, 7; (animal) pl. O. f. 3. 
Animal suborbicular, white; mantle partially closed and 
with only two apertures ; the anterior is the anomalous tubular 
projection, which is not entire as in KX. suborbicularis, but slit 
open at the base, and serves as a passage for the foot. When 
the animal marches it is generally pushed therein, displacmg 
the sides of the scission, which on its withdrawal assumes the 
aspect of an entire tube. This combined pedal aperture and 
tubular appendage is divided by a septum from another con- 
siderable fissure in the mantle, from which the points of the 
branchiz are visible; through it the water to supply the 
vital principle reaches them, and when effete is expelled by 
the channel at which it entered; the anus is a sessile orifice 
completely within the sht of the mantle, and discharges 
therein; in fact, the fissure is the entrance of a common 
cavity that serves to admit the branchial water and receive 
the rejectamenta before exclusion. The anterior tube bemg 
nothing more than an open protrusion or continuation of the 
mantle, some water may reach the branchiz through it, and 
be expelled therefrom in combination with the strict pedal 
aperture ; but its principal use, as we have shown in K. sub- 
orbicularis, is to act as an organ of reproduction to convey 
water to the pulli in the matrix, which from their dorsal posi- 
tion could not well receive it without the aid of such an 
