'Pond-snails 



I'^l 



home and eastern counties. Tlience it extends to 

 Hampshire, Somerset, Dorset, and Gloucester ; 

 Oxford, Norfolk, Cambridgeshire, Northamptonshire, 

 Worcester, Warwick, and Stafts. It also occurs in 

 Ireland, Scotland, and Wales. The Margined Trumpet- 

 snail (P. umhilicatiis), though much like 

 the last named, is larger, thicker, and 

 more plentiful. The whorls are narrower, 

 and the keel instead of being anywhere 

 near the middle is placed at the lower 

 edge, so that it forms a very distinct 

 margin round the disk viewed from below as in the 

 figure. All these four species are inactive, irritable, 

 and fond of floating on the surface. 



The next group of these Trumpet-snails consists of 

 three minute species that agree in their shells having 

 few whoi'ls. Of these the Glossy Trumpet-snail 

 (P. glaher) is not so glossy as its name implies, except 

 in contrast with the following species, but it has 

 sometimes even an iridescence. It is little more than 

 one-eighth of an inch across, greyish brown, convex 

 above with a depressed centre, and concave below 

 with a large deep umbilicus ; the mouth is almost 

 round. It occurs in ponds and marshes, but is 

 very local, though widely distributed. The White 

 Trumpet-snail (P. alhits) is much like it, but the shell 

 is larger (one-quarter of an inch across), whitish grey in 

 colour, and all pretensions to gloss are destroyed by 

 close-set spiral ridges. The upper-side is convex, the 

 lower concave with a large umbilicus. The mouth 

 is more oval than round. It occurs in similar situa- 

 tions to the last, but is not nearl}^ so local. Tlie 

 strong spiral ridges at once serve to identify it. The 



