116 hey: mollusca of Derbyshire. 



P. vivipara. — Very plentiful in the same canal, where it grows 



to a large size, and may be found quite close to the town 



of Derby. Although I have taken hundreds out of the 



water for examuiation with the hope of finding P. contecta, 



I have as yet failed. 

 Bythinia tentaculata. — Occurs very commonly in all the 



canals and in most ditches. 

 B. leach ii. — Occurs fairly commonly in the Shardlow Canal, 



at Weston-on-Trent, and in the Black Pool, which is a 



back-water from the Trent and a splendid hunting ground. 

 Valvata piscinalis. — Common all over the district, 

 Planorbis albus. — Fairly distributed in canals at Weston, 



Willington, Chellaston near Derby, Little Eaton, &c. 

 P. spirorbis. — I find this abundant in ditches at Little Eaton, 



Alveston, near Derby, and at Weston-on-Trent. 

 P. vortex. — Occurs in the same localities and is quite as common. 

 P. carinatus. — Very plentiful in the same localities as P. 



spirorbis and P. vortex. 

 P. complanatus. — Certainly the commonest of the genus in 



this locality ; it is very plentiful in all the ditches in the 



low-lying country. 

 P. corneus. — This I find fairly plentiful in all the canals; 



some specimens attain to a large size. 

 P. contortus. — I find a few specimens at most places; Weston 



Canal, Black Pool and ditches. Little Eaton Canal and 



ditches, Cromford Canal, &c. 

 Physa hypnorum. — As yet I have only found a few specimens, 



in the canal at Little Eaton. 

 P. fontinalis. — A very common species, and in one ditch at 



Alvaston, near Derby, it can be seen in thousands and 



gathered a scoop full at a time ; it also occurs in canals and 



ditches at Little Eaton, Willington and Weston, Sinfin 



Brook, &c. 

 Limnaea glutinosa.- — Very scarce (as yet) ; only found two 

 specimens in Sinfin Brook, near Derby. 



J.C., vi., July, 1889 



