92 KELLIADJj]. 



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 in 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. RUBRA, Montagu. 



K. rubra, Brit. Moll. ii. p. 94, pi. 36. f. 5,6,7; (animal) pi. 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 K. suborbicularis, but slit 

 open at the base, and serves as a passage for the foot. When 

 the animal marches it is generally pushed therein, displacing 

 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 

 branchiae 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 slit 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 being 

 nothing more than an open protrusion or continuation of the 

 mantle, some water may reach the branchiae 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 



