COOPER AND LOTDELL : MIDDLESEX MOLLUSCA. 231 



97. Sph^rium rivicola (Leach). 



Canal at Yiewsley, Thames at Hampton Wick and Shepperton, 

 Brentford, Grand Junction Canal near Willesden, River Lea at 

 Tottenham, canal at Edmonton and Ponders End. It is also recorded 

 for Hendon (C. C. Fryer, S.G., 1889, p. 259). 



Var. flavescens, Moq. Grand Junction Canal near Willesden, and 

 River Lea at Tottenham. 



98. Sph^rium corneum (L.). 



Common and widely distributed. 



Yar. pisidioides, Gray. Paddington (B.C., i, p. 6) ; Regents Park 

 (Rim., p. 4). 



Var. scaldtana, Norman. River Brent near Hendon, and canal at 

 Yiewsley. It is also recorded for Hampstead (Rim., p. 3). 



Var. nucleus, >Studer. Finchley ; also from Hampstead and Hendon 

 (Rim., p. 3). 



Yar. J^avescetis, Macg. Moat at Finchley, and occasionally with the 

 type in other localities. 



99. Sph^rium lacustre (Miill.). 



Harefield, Frayswater at Uxbridge, Staines, Bushey Park, Hendon, 

 Neasden, Perivale, Willesden, Fulham, Finchley, Hampstead, Stanmore, 

 and Enfield. Widely distributed, but not a common species. 



Var. Brockotiiana, Bgt. Hornsey (Rim., p. 6). 



100. Sph-^rium pallidum. Gray. 



Recorded from the Grand Junction Canal (" Paddington Canal ") near 

 Kensal Green in 1856, when it was described by Dr. Gray (Ann. Mag. 

 Nat. Hist., ser. ii, vol. xvii, p. 465). We are not aware of its having 

 been taken in Middlesex in recent years. 



101. PiSIDIUM AMNICUM (Miill.). 



In all the rivers and many of the canals. A small, solid, sub- 

 triangular form lives in the Thames at Hampton Wick. 



102. PisiDiTJM supiNUM, A. Schmidt. 

 Thames at Hampton Wick and Twickenham, stream at Bedfont. 

 This species is well known as a Holocene fossil in the Thames Valley, 

 but (with the exception of a few shells in the Gray Collection at 

 South Kensington labelled "Battersea") it does not appear to have 

 been taken alive in this country hitherto. At Hampton Wick it lives 

 in sand ; at Twickenham and Bedfont it occurs very sparingly in mud. 

 Compared with P. suhtruncatum the shell of this species is usually 

 more sharply triangular, the beaks are very prominent, and often have 

 an appendiculum similar to that of P. Hensloivianum. A variety is 

 more oval in outline; in all cases the shell is much more solid than 

 in any of our other small Pisidia, and the teeth are stronger. 



103. PisiDiuM Henslowianum (Shepp.). 

 Frayswater at Uxbridge, Acton, Bedfont, Bushej^ Park, Thames at 

 Twickenham. Also from the Red Arches Pond at Hampstead (B. B. 

 Woodward), and AVest Drayton (W. M. Webb). 



