100 KELLLUm 



cardinal tooth, is separated from the central tooth by a 

 narrow cavity. 



Few examples exceed half an inch in length, and about 

 three-eighths of an inch in breadth. 



At the meeting of the British Association at Oxford, in 

 1847, the following interesting particulars respecting this 

 Mollusk were communicated by Mr. Alder : — 



" When lately dredging in Fowey Harbour, I fortunately 

 met with a living individual of this rare genus, the Lepton 

 squamosum, which I have kept alive for a fortnight, and am 

 thus enabled to supply some account of its characters and 

 habits. The animal has proved very interesting, on account 

 of its variation from the usual form of the bivalve Mollusca. 

 It is of a transparent white. The mantle is very large, and, 

 when fully extended, is at least one-third larger than the 

 shell, passing considerably beyond it in the free part, which 

 is thin and transparent, with a smooth undulating margin. 

 Between this and the shell there is a fringe of filaments, 

 extending completely round to the umbones, but largest 

 and most conspicuous on the back. There is, however, a 

 single filament, much stouter and longer than the rest, 

 which, when the animal is crawling, is waved to and fro, 

 like a tentacle, apparently feeling the way as it goes. The 

 other filaments are comparatively motionless, floating loosely 

 in the water, though capable of being thrown out or with- 

 drawn, at pleasure. The mantle is open for about three- 

 fourths of its circumference, being united for a short space 

 before and behind : in the latter part it forms a short 

 siphon, with a single aperture. The foot is very large, 

 rather thick and tapering in front, with a slight nipple-like 

 termination ; behind, it extends into a long pointed heel, 

 with thin margins, which are divided for about half the 

 length of the base, forming, in that part, a kind of disc, the 



