SPH^RIUM. 9 



Mr. Daniel says that he found this species in the Grand 

 Surrey Canal some years before it was noticed by Dr. 

 Gray, but that he then considered it to be a variety of 

 C. rivicola. It is found in company with all the other 

 species of Sphcerium. A living specimen, which had been 

 taken early in February, and kept in a vessel by itself, 

 gave birth about three weeks afterwards to some young 

 ones at intervals of two or three days. Immediately on 

 being excluded, they were very active, and used their long 

 foot as an organ of progression, by extending it to its full 

 length ; and, after attaching its point to the bottom of 

 the vessel, like a leech, they drew up their shell to it; and 

 by repeating this several times they contrived to travel 

 along for some little distance. They seemed to be fond 

 of nestling under their mother for the sake of shelter or 

 shade. 



There cannot be much doubt that this elegant and 

 very distinct species is the same as that which Drapar- 

 naud, in his ' Histoire naturelle des MoUusques ter- 

 restres et fluviatiles de la France ^ (p. 130, pi. x. f. 6, 7), 

 described and figured under the name of Cyclas lacustris. 

 He distinguished it from S. corneum and S. invicola by 

 its being " plus mince, plus transparente, plus pale et 

 beaucoup plus aplatie." His description of the beaks 

 and hinge also exactly agrees with that of our species ; 

 and the very different terms in which he characterized 

 his C. caliculata preclude our supposing that this accu- 

 rate naturalist could have taken for it a variety of the 

 last-named species. Ferussac, being aware of the error 

 which Draparnaud had committed in referring the spe- 

 cies in question to the Tellina lacustris of Miiller, gave 

 it the appropriate name which I have now adopted. The 

 species appears, however, to have been lost in France ; 

 and all the continental conchologists have applied the 



B 5 



