POND AND RIVER SHELLS. 43 



globular, with a more conspicuous ligament. The 

 two are often found together, and well-known locali- 

 ties for them are the Grand Junction Canal at Pad- 

 dington, the Thames shore at Battersea, Richmond, 

 and Clifden Hampden, the ponds on Wandsworth 

 and Clapham Commons, and the marshes below 

 London. A third species, Sphcsrium ovale (PI. V., 

 fig. 2), has been found by Mr. Gwyn Jeffreys in 

 the Paddington Canal, and, under the name of 

 S. pallidu'm, it was figured and described by Dr. Gray 

 (Ann. Mag. Nat. Hist., xvii. p. 465) from specimens 

 procured in the canal near Kensal Green. Some 

 years previously, however, it had been met with in 

 the Surrey Canal, but at the time it was supposed 

 by the discoverer, Mr. Daniel, to be a variety of 

 S. rivicola. It certainly resembles this species more 

 than any other, but may be distinguished by its 

 oblong and almost angular shape, thinner shell, and 

 paler colour. 



A nearly allied genus is Pisidium, of which there 

 are five recognizable British species — amnicum and 

 fontinalc, with triangular- shaped shell ; pusillum, 

 oval; nitklum, round; and roseum, oblong — the 

 three first named of which have all been met with 



