of the District aronnd Colchester. 91 



V. CRisTATA, Miill. — I find this species is more frequently 

 an inliabitiint of ponds than V. piscinalis. It occurs every- 

 where throughout the district, and is one of the shells chosen 

 frequently by a Caddis-worm to form its case. 



Planorbis lineatus, Walker. — I have seen shells said to 

 have been found in the Stour within my boundaries, but 

 have never taken the species myself. 



P. NiTiDus, Miill. — Occurs in many parts of the district 

 both in slow streams and ponds, but it is not frequent. 



P. NAUTiLEus, Linn. — No doubt is frequently passed over 

 from its small size. I find it sometimes very abundantly in 

 ponds at West Bergholt. Var. criUata occurs in the same 

 spots, and is, I think, one of our most beautiful shells. 



P. ALBus, Miill. — Abundant where it occurs, but occasionally 

 for years it seems almost to die out in some ponds. It is 

 found on all soils : also in brackish water on the marshes 

 near Wyvenhoe Park. 



P. spiRORBis, Miill. — Very abundant. I have found several 

 distorted specimens in which the whorls are more or less 

 separated or displaced. 



P. VORTEX, Linn. — Not quite so abundant as the last 

 species, but found all over the district. 



Var. compressa. — Occasionally in the marshes of the Colne. 



P. CARiNATUS, Miill. — I find this snail more frequently in 

 the marshes by the rivers and brooks than in stagnant 

 ponds. It is said never to be plentiful, but I once found a 

 shallow pond near Ardleigh Crown swarming with it. 



P. coMPLANATUs, Limi. — Common throughout the district. 



P. coENEus, Linn. — I never find this mollusk in ponds 

 unless they are in the marshes and connected with the 

 rivers ; there they are fairly plentiful. The largest speci- 

 mens I have seen were reared in a soft-water butt, at 

 Wormingford. 



P. coNTORTus, Linn. — Common in our rivers and ponds of 

 stagnant water in many parts of the district. 



Physa hypnorum, Linn, — Very local and rare. An occasional 



