12 



by the sun as scarcely to show the marks of any foot- 

 steps on it. 



This differs from all the other species of Sphcerium in 

 the shell being rounder and of a subquadrate form, its 

 great tenuity, and especially in the singular caps or ca- 

 lyces which surmount the beaks. 



I cannot agree with the learned authors of the ' Bri- 

 tish Mollusca' in preferring Draparnaud's name of 

 caliculata to that which had been long before assigned 

 to this species by Miiller. The description given by the 

 illustrious Danish naturalist does not appear to me at all 

 deficient in that accuracy and precision which characterize 

 all his writings ; and if some continental authors have 

 erroneously confounded this species with the Cyclas la- 

 custris of Draparnaud, this cannot be a sufficient reason 

 for continuing the mistake. At any rate, the best French 

 authorities (including Ferussac, Blainville, and Moquin- 

 Tandon), as well as nearly all the conchologists of our 

 own country, have adopted Miiller 's name in preference 

 to that of Draparnaud. 



Although Mr. Jenyns has, in his excellent Mono- 

 graph, given an interesting notice of the habits of this 

 mollusk in a state of confinement, some further details, 

 which have been communicated to me by my friend 

 Dr. Lukis, of Guernsey, of its natatory, spinning, and 

 other performances, may not be unacceptable. In one 

 of his letters to me he says, "I placed a number 

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

 sluggish stream in which they were captured. In a 

 short time they commenced 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 climb- 

 ing the sides of the globe, and rarely missing their foot- 



