294 

 PISIDIUM SUPINUM A. Schmidt LIVING IN THE THAMES. 



By T- E. cooper. 



(Read before the Society, February loth, 1909). 



Pisidium siipiiium has been known for six or seven years as a Holo- 

 cene fossil in the valleys of the Thames and the Lea. The earliest 

 notice of it as British is, I believe, in the Essex Naturalist, April, 

 1903. In the Gray Collection at South Kensington there are a few 

 recent specimens labelled " Battersea," but with this exception it 

 does not appear to have been taken alive in this country until last 

 year when I found it living in sand in the Thames at Hampton Wick. 

 It occurs there in fair numbers ; it also lives sparingly in mud at 

 Twickenham, and in a stream at Bedfont. It will probably turn up 

 elsewhere. 



For the identification of this shell, I am indebted to Mr. B. B. 

 Woodward, F.G.S., who has made a special study of Pisidium. The 

 shell of P. supinum is much more solid for its size than any other 

 British Pisidium. The typical form is sharply triangular, with very 

 prominent beaks. It often — but not always — has an appendiculum, 

 similar to that of P. hensloivianum. The hinge teeth are strong, as 

 it lives in running water. At Hampton Wick its companion is P. 

 amnicum. 



Mr. J. W. Taylor writes me, under date 21st December, that he has 

 just detected this Pisidium among some Lincoln shells. 



Shell-Collecting in the Barmouth District. — The district round Barmouth 

 is not exactly the iinest collecting-ground for the conchologist with only a week at 

 his immediate disposal, but several species are nevertheless to be discovered by the 

 patient searcher. On the hill behind the somewhat straggling town Htlix nemoralis 

 and H. hoiiensis are to be found, and on the wall sf the Llanaber Road, near the 

 Catholic Chapel, is a flourishing colony of Helix aspersa. All the larger Helices 

 are furnished with rather thin shells. Some rather large Pyrainidiila rotutidata 

 are also in the vicinity of the same road. Hygroniia hispida and Helicetla capet-ata 

 occur somewhat sparingly near the viaduct ; Vitrea nitidiila and V. cellaria to- 

 gether with V, rogersi (the last a new record for Merionethshire) are to be found 

 on the walls ; Jaminia cylindracea is common, and Linincta iruncatula is to be 

 gathered (small in size) from a rock pool in the vicinity of the Episcopal Church. 

 At Arthog, a few miles away on the south side of the estuary, Pyratnidula rotundata 

 is common together with Vitrea rogersi and Cochlicopa liibrica ; whilst Jaminia 



