Mr. Jeffreys on Lepton sulcatulum. 131 



XIV. Note in answer to Mr. Clark's Remarks on Lepton sulca- 

 tulum. By J. GWYN JEFFREYS, Esq., F.R.S. 



To the Editors of the Annals of Natural History. 

 GENTLEMEN, 



I cannot agree with Mr. Clark in supposing that Lepton sul- 

 catulum is the fry of Circe minima. I have now before me no 

 less than 49 perfect specimens (some of which retain the remains 

 of the animal) and 332 single valves of the former species. 

 They constitute a perfect series from the fry to the adult. I 

 have placed in juxtaposition with them a complete series of 

 Circe minima obtained from the same locality (Guernsey), three 

 of the latter being considerably smaller than the average size of 

 Lepton sulcatulum. Each series differs widely from the other in 

 respect of form, texture, dentition, and position of the ligament. 

 The fry of Circe minima is gibbous, of a triangular shape, re- 

 markably solid for its size, with its beaks strongly incurved, and 

 a distinct lunule under them ; and it possesses an external liga- 

 ment and the peculiar dentition of the CyprinicUe. The Lepton 

 sulcatulum, on the contrary, is somewhat compressed, nearly 

 round in outline, semitransparent, with its beaks calyculated 

 (as in the other species of Lepton), and it has an internal liga- 

 ment and the unmistakeable dentition of the Kelliada. Even 

 in the most minute Circe minima the coloured spots and mark- 

 ings which adorn the adult are observable ; while the other is 

 white and spotless. The number of ridges, too, on the first are 

 not half so numerous as those on Lepton sulcatulum, and they 

 are disposed in a very different way. Owing to the ligament in 

 Lepton being internal, the valves become easily separated ; and 

 this accounts for the comparatively small proportion of perfect 

 specimens which are usually met with. I request your readers 

 to take the trouble of comparing the excellent figures of the 

 hinge in Lepton sulcatulum (from a drawing kindly furnished by 

 my friend Dr. Lukis) in the ' Annals ' ser. 3. vol. iii. pi. 2. f. c, d, 

 e,f, with those of Circe minima in the ' British Mollusca/ vol. iv. 

 pi. 26. f. 4, and I think they will at once be satisfied that I 

 have not erred in considering these species to be distinct. 



Before I described Lepton sulcatulum in the 'Annals,' I bad 

 the advantage of a correspondence with Mr. Clark on the sub- 

 ject, in which he at first pronounced the shells I sent him, as 

 belonging to a new species, to be successively Lucina borealis, 

 L. leucoma, L. spinifera, and Venus casina; but afterwards he 

 candidly admitted that " beyond all dispute" it was a Lepton, 

 and allied to L. Clarkice. His observations on the last occasion 

 were extremely valuable and interesting, especially as to the 



