VALVATxi. 73 



Var. 3. aciimhiata. Shell having the spire still more pro- 

 duced, and ending in rather a sharp point. 



Habitat : Slow and still waters throughout the Bri- 

 tish Isles ; common in our upper tertiary beds. Var. 1 

 occurs also in various parts of the kingdom ; but it is 

 more locals and not found with the typical form. The 

 young of both these forms have invariably the spire pro- 

 portionably more depressed than in the adult. Var. 2. 

 Grassmere ( J. Gr. J.) . This somewhat resembles the well- 

 known form called " antiqua ^' by Professor Morris, from 

 the upper tertiary deposit at Grays. Var. 3. Avon R., 

 Bristol (J. G. J.) ; North of Ireland (Mrs. Puxley). Spe- 

 cimens of the typical form, which Mr. Bridgman pro- 

 cured and kindly sent me, from brackish water at Lynn, 

 are much thicker and of a darker colour than usual, .and 

 have stronger striae ; and the opercula have fewer whorls 

 and slighter ridges. In another variety which I have 

 received from my valued friend and correspondent, Mr. 

 Waller, and which he found at Finnoe, Co. Tipperary, 

 the shell is more conic and the spiral ridges form irre- 

 gular white lines. A monstrosity has also occurred to 

 me, in which the spire is twisted to one side. This spe- 

 cies ranges from Siberia to Naples. 



In May, June, July and August the eggs of this mol- 

 lusk are deposited on various substances, and sometimes 

 on the shell of a Planorbis. They are united in a gela- 

 tinous mass, and enclosed in a globular capsule having a 

 short stalk, by which it is attached. The eggs contained 

 in each capsule number, according to Bouchard-Chante- 

 reaux, from 60 to 80 ; but Moquin-Tandon, who appears 

 to have observed many cases of such egg-laying and 

 -hatching in an aquarium, states that out of 19 capsules 

 the number of eggs in each varied from 4 to 24 only. 

 When the eggs have come to maturity, which is about the 



