SWANTON : LAND AND FRESHWATER MOLLUSCA OF SOMERSETSHIRE. 24I 



Sphaerium corneum L. — Very common. 



Var. flavescens Macgill. — Clevedon (Cundall). 

 Var. nucleus Studer. — Clevedon (Cundall). 

 Var. scaldiana Norman. — Bath (Rich). 

 Var. pisidioides Gray. — River Avon, Bath (Jordan). 

 Sphaerium lacustre Mull. — Local, frequenting ponds. Bath 

 (Bristol Mus.) ; Jenyns coll. (as S. calyculaturn) (Bath Mus.); Avon- 

 mouth and Ham Green (Cundall) ; Clevedon Hill (Norman) ; ponds 

 at Bratton St. Maur, Wincanton (E.W.S.). 



Sphaerium rivicola Leach.— Local. Bath Canal (Bath Mus., 

 Bristol Mus.) ; Keynsham, Kennet, and Avon Canal (Cundall); river 

 Cale at Harwood below Wincanton (Galpin). 



* Sphaerium pallidum Gray. — Jenyns coll. (Bath Mus). ; Kennet 

 and Avon Canal (Cundall). Apparently confined to the river Avon, 

 for I find no other records. 



Pisidium amnicum Mull. — Widely distributed in ponds and 

 ditches. 



Pisidium fontinale Drap.— Widely distributed. " Common on 

 the moor between Clevedon and Portishead " (Norman) ; frequent 

 in the Wincanton district. 



Var. henslowana Shepp. — Leigh Woods, and Kennet and 

 Avon Canal (Cundall) ; Clevedon (Norman). 



Var. pulchella Jenyns. — Jenyns coll., labelled as a species 

 (Bath Mus.); "in the larger and clearer of the rhines not un- 

 common ; fine in West Mead Rhine, Yatton " (Norman). 



Var. cinerea Alder. — Kenn Moor (Norman) ; Kennet and 

 Avon Canal (Cundall) ; Bath (Clark). 



Pisidium pusillum Gm. — A rare species. Jenyns coll. (Bath 

 Mus.) ; Avonmouth and Bedminster (Cundall). 



Var. obtusalis Lam.— Avonmouth (Cundall); in a ditch near 

 the Pill, Clevedon (Norman). 



Pisidium nitidum Jenyns. — A very rare species. The only 

 record is "'a large pond by the side of the railway at the third (?) 

 bridge from Clevedon" (Norman). The same locality from which 

 Norman recorded another rare species, Planorbis parvus Say (E.W.S.). 

 Dreissensia polymorpha Pall. — An extremely local species. 

 Jenyns coll. (Bath Mus.) ; Bath Canal (Mrs. Oldroyd) ; river Avon 

 and Avon and Kennet Canal near Bristol (Cundall). It being an 

 alien species, we here give in toto Norman's note upon it : — 



" The late Mr. Hugh Strickland, in a paper published in Loudon's 

 Magazine of Natural History, new series (vol. ii.), 1838, p. 361, on 

 the ' Naturalisation of Dreissena in England,' states that this shell has 



p 



