122 



is difficult to acknowledge it as merely a variety. In the 

 first place it is considerably larger, being 5^ lines, 

 whilst the other form does not exceed 3| lines. In the 

 second place the body whorl is more tumid, there are 

 five convolutions, and the spire is produced; whilst in 

 the ordinary form there are but four convolutions, and 

 the spire scarcely elevated above the body whorl. In 

 the third place the colour is that of very pale horn with 

 a broad white band, whilst in the ordinary form it is 

 amber-coloured and devoid of this white band. Some 

 authors have tried to explain this difference to situation, 

 stating that the one form is found in plashes of water, 

 whilst the other is in deeper water. This explanation, 

 however, is not bourn out by investigation. The form 

 acuta is found in a clear deep brook, amongst water 

 plants, in which the other form of Physa fontinalis is 

 also found associated with it. The latter form is an in- 

 habitant of the Trent, clear brooks, and stagnant 

 ditches. There is another peculiarity in the acuta, it 

 has a more acute tail, and tosses its shell about re- 

 peatedly in an extraordinary manner, as if it would 

 |hrow it away. Some conchologists who have noticed 

 this fact consider it to be infested by a minute worm, 

 known as the Gordius inquitinus of Miiller. 



The colour of the animal is greyish, and the mantle 

 edge is reflected over the shell. 



An abundant and generally diffused species, inhabit- 

 ing ponds, ditches, rivers, and lakes, on aquatic 

 vegetation. 



M. Bouchard Chautereaux says it deposits from three 

 to ten eggs at a time, which are hatched in 16 days. 



The localities in this neighbourhood in which this 

 shell have been found abundantly are, dikes in Lenton, 

 Beeslon, Radford, and Oxton, the Musco-sic dike, the 

 dike below Broad-gate, ponds at WoUaton, and 



