LUCINA. 85 



to show a minute terminal perforation. This metamorphosis 

 is probably effected through its elasticity, and being distended 

 with water. In the large specimen, of which this is the de- 

 scription, the animal was more apathetic than the small one 

 of the first part of these notes ; the foot was never protruded, 

 and of course no siphons, as none exist ; the only movement 

 for forty-eight hours was a central opening to admit the 

 branchial water, and the exsertion of the margins of the 

 mantle, which are quite plain. 



We have here the decided foot of the typical Lucince, 

 agreeably to the descriptions of M. Poli and M. Valenciennes ; 

 but if the latter is right as to there being but one branchial 

 lamina on each side, in all the true Lucinte, our present spe- 

 cies, which beyond doubt has two on each side, would be an 

 aberration from the typical Lucina, though so closely allied to 

 it by the foot, which is of so singular configuration, that we 

 think it a generic characteristic of far greater value than the 

 single branchial plate on each side, which form prevails in all 

 the Anatinae, and in some of the Tellina. We therefore 

 would prefer to place this animal as a Lucina, even if it should 

 turn out that all the Lucince have but one branchial lamina, 

 which fact at present is by no means to be depended on ; we 

 consider the character of the tubular foot to be more worthy 

 and important, in this case, than that of a singularity in the 

 structure, or rather in the disposition, of the respiratory organ; 

 and as to the branchial plate being a single one, it is more so 

 in appearance than in reality, which is fully explained in the 

 notes on Anatina phaseolina. In this very delicate animal 

 we could not trace the connection of the foot with the viscera 

 of the body, if it exists. M. Valenciennes says, that the water 

 from the foot must enter and mix with the splanchnic con- 

 tents ; we greatly doubt this fact, and refer for our reasons to 

 the preliminary observations on the Lamellibraiichiata. 



L. BOREALIS, Linnaeus. 

 L. borealis, Brit. Moll. ii. p. 46, pi. 35. f. 5, and (animal) pi. M. f. 6. 



Exmouth, 2nd June, 1852. 

 This day a live specimen, about fths of an inch diameter, 



