132 Mr. W. Clark on the genus Lepton. 



test ; with respect to its congener, the L. nitidum, it has been 

 stated that it is smooth and without punctures : this is a mistake, 

 as I can show fifty specimens not only well-marked on the 

 greenish epidermis, but in the substance of the shell. 



I have the satisfaction to state, that I have observed another 

 live L. squamosum, and also obtained full notes of the animal of 

 one of our great desiderata, the L. nitidum, from a most lively 

 animal, which for several days gave me every facility for exami- 

 nation. The jL. squamosum, just alluded to, was kept thirty-four 

 days in a glass of sea-water, changed daily, and was apparently 

 as vigorous as when first placed in captivity ; it thus appears 

 that the Conchiferse can exist for a long time in pure sea-water, 

 on the animalculse it contains, though that aliment may not be 

 their sole resource in freedom. 



I may observe, that the habitude of crawling and swimming 

 with the foot uppermost in Lepton, and in several other minute 

 bivalves, perhaps in all, shows the close alliance of the Acephala 

 with the Gasteropoda, all of which, in their minute condition, 

 have precisely the same peculiar system of dorsal natation. I 

 ought to have mentioned that the liver is light green and mixed 

 up with a flake-white ovary ; but from the extreme tenderness of 

 the branchiae, I cannot speak of them and the palpi with certainty 

 as to form and number. 



July 2nd. — As I had just finished the above, a lively specimen 

 of this species was met with, which, on being placed in water, at 

 once unfurled its long and beautiful fringes, and exserted the 

 ample niveous mantle and foot. This is certainly the Prince of 

 British bivalves ; the snow-white colour of both animal and shell 

 sheds over this interesting creature the inexpressible charms of 

 purity and elegance. It now lives in the same vase with its 

 pigmy congener, the L. convexum. 



Lepton nitidum, Turton et auct. 



The animal inhabits a light greenish yellow or pure white, 

 subrhomboidal, moderately convex, more or less punctured shell. 

 The mantle is frosted white with the margins plain, but as much 

 proportionately protruded beyond the edge of the shell as in 

 L. squamosum', it is in like manner clothed with cirrhal filaments 

 of about the same length, and of pruinose white, but unlike that 

 species, they are rather less developed dorsally than ventrally ; 

 each filament at its terminal edge is studded with four or five 

 white points or cilia, so sharp and minute as to require a 

 powerful lens to see them. There is no conspicuous leading pro- 

 cess, as in the preceding species, but the mantle, at the same 

 anterior point, forms a visible projection or fold. In this spe- 



