hand-snails 371 



kinds, whicli gets picked up Ijy tlio slime. The 

 process several times repeated, the shell soon bears no 

 resemblance to itself. The young of B. immtanus 

 sometimes co^'ers itself in the same way, as does the 

 young of the next species. 



The snails of the genus Piqm are elongated like 

 those of Bidiniiniis, but the spire ends in a short 

 point. The mouth, which is usually horse-shoe shaped, 

 or half-oval, is guarded by teeth or spiral plaits or 

 folds. Some of the animals have the lower pair of 

 tentacles in a rudimentary condition, or they are 

 altogether wanting; these are sometimes separated 

 to form another genus, Vertigo. There are fourteen 

 native species, and most of these are so minute that 

 we shall not attempt to give distinguishing descrip- 

 tions of each, but a list of them will be found in the 

 Appendix. They are social in their habits, and where 

 one or two specimens are found a slight search will 

 soon be rewarded by the discovery of others. Old 

 mossy walls with crevices, stone dikes, the loose bark 

 of trees, and among moss, are the favourite resorts of 

 these Chrysalis-snails. 



The Large Chrysalis-snail (P. secale) is only large 

 by comparison with the others ; it is about one-third 

 of an inch in length. There are eight or nine 

 yellow-brown whorls, of which the last four 

 are of pretty equal width. The mouth is 

 largely occupied by eight or nine tooth-like 

 extensions of the thickened lip. It is a local 

 form, found on rocks and in woods in England 

 only, and chiefly in the south. P. cylindracea 

 is the most widely distributed of the genus. It is about 

 one-seventh of an inch long, almost oval in form ; the 



