FAMILY CARDIACEA. 



239 



The animal of C. cornea is of a dingy white, with the siphonal 

 orifices tinged with flesh-colour. In a drawing of Mr. Berkeley's 

 now before me, they are quite pink, while the foot is white. It 

 has the habit of floating on the water by means of the under surface 

 of the foot like Physa. 



M. Moqiiin-Tandon describes the variety named by M. Normand 

 Scaldiana as being larger and ruder, with the umboes more inflated, 

 and offering a passage towards C. rivicola, especially in having the 

 ligament partially external. 



3. Cyclas Pisidioides. Pisidium-like Cyclas. 



Shell ; oblong-oval, subtriangular, thin, ventricose, concentrically 



finely ridged, bluish-white, covered with a 



glossy yellowish-olive epidermis, inequilateral, 



rounded in front, produced into a broad sub- 

 angular slope behind, umboes moderately 



convex. 

 Sphcerium Pisidioides, Gray (1856), Ann. Nat. Hist. 



2nd series, vol. xviii. p. 25. 

 Cyclas Pisidioides, Gray (1857), Turt. Man. p. 255. 

 Sphcerium corneum var., Jeffreys (1862), Brit. Conch. 



p. 6. 

 Sab. Padclington Canal. 



I give this species quantum valeat. If, as Mr. 

 Jeffreys states, it is a variety of C. cornea, in which 

 the posterior side is more than usually produced 

 into a slope, the concentric striae coarser, and the 

 ligament slightly perceptible on the outside, it is 

 a very extreme variety. These are features partaking more of the 

 character of C. rivicola, and my example of C. Pisidioides, here 

 figured from the collection of Dr. Battersby, has more the appear- 

 ance of that species than of G. cornea. It was described in 1856 

 from specimens collected in the Paddington Canal. 



Dr. Gray describes the animal of Cyclas Pisidioides as having 

 the siphons united nearly to the end, the upper shorter, subconic ; 

 orifices circular, simple, the lower rather large, about twice the 

 length of the upper when expanded. 



