Mr. Jeffreys on British Mollusca. 35 



it has some analogies with the genus Codakia of ScopoH. Even this 

 tiny shell is sometimes found to have been drilled by one of the 

 canaliferous mollusks. 



Galeomma Turtoni, ii. 105. Weymouth, in Eschara foliacea 

 {Mr. Thompson). 



Sphaerium calycalatum. Cyclas calyculattty \\. 115. Plymouth 

 {Rev, Mr. Norman). Scopoli's generic name ought, I think, to be 

 retained, as it was indicated by him, so long ago as 1777, with suffi- 

 cient precision, and the type which he gave {Tellina cornea of Lin- 

 naeus) is unmistakeable. I believe it is not generally known that the 

 Sphceria and Pisidia possess the power of swimming and floating on 

 the ^<?^«?e/•-surface of the water. M. Moquin-Tandon, indeed, in his 

 admirable work on the Land and Freshwater Mollusca of France, 

 says, with regard to the Cyclades, " Ces moUusques rampent tres 

 bien sur les plantes aquatiques et meme a la surface de I'eau, au 

 moins pendant leur jeunesse." And he says, with regard to the 

 Pisidia, " Les Pisidies rampent avec facilite ; elles executent meme 

 des especes de sauts. On assure que, dans certaines circonstances, 

 elles se tiennent a la surface de I'eau et peuvent y nager." And 

 M.Baudon, in his excellent Monograph on the French Pisidia, gives 

 an interestnig account of the mode of progression adopted by the Pi- 

 sidium. But I think it will be also interesting to have Dr. Lukis's 

 account of the natatory feats of the Sphcerium calyculatum, as well 

 as of a curious phsenomenon resulting from the passage of a conti- 

 nuous stream of water through one or both of its siphonal tubes. 

 He says, in a letter to me dated the 27th of October last, '' I placed 

 a number in a small fish- globe in clear water taken from the sluggish 

 stream in which they were captured. Tn a short time they com- 

 menced crawling about and actually ascending the slippery concave 

 glass. In a few days a considerable number of the fry had been cast, 

 which proved far more active than their parents, readily climbing the 

 sides of the globe, and rarely missing their footing, while the adults 

 made many ineffectual attempts ; but both fry and adults, when they 

 reach the edge of the water, take to the surface easily, and creep 

 along slowly and apparently cautiously, as if in search of some 

 floating substance, near which they will rest for hours. The exserted 

 foot moves, during this under-surface progression, by a gentle vermi- 

 cular action, the siphons being at the same time protruded. The 

 foot during repose is usually retracted, and does not seem necessary 

 for mere floating purposes. I have not been able to detect any fila- 

 ment, as in Kellia,'' &c. And he adds, "An interesting httle scene 

 occurred in the globe the other evening. Several individuals had 

 reached a few leaves and hanging roots of minute water-plants which 

 floated in the centre of the globe, down the stems of which three or 

 four had crept to a depth of about an inch and a half. There they 

 reposed : but they were not absolutely motionless, for to my surprise 

 the whole group, plants and all, were dreamily enjoying the delights 

 of a short, but long-contiimed, rotation. Round and round they 

 all together went, — a little world revolving from some unseen cause, 

 and leaving this for me to conjecture. At first I thought some mi- 



3* 



