Tond-snails 3 1 9 



separated from the Limnseids because the mantle has 

 a contractile expansion, which is usually turned up 

 until it almost entirely hides the shell. In this con- 

 dition it presents the appearance of a little dab of 

 glue, whence the name. As one might expect froin 

 our study of certain marine species that cover up 

 their shells in this manner, the globular shell is 

 reduced to the utmost possible thinness, and the spire 

 is exceedingly abbreviated. It is an active mollusk, 

 and has a strange habit of disappearing for long 

 periods from its known localities, and as suddenly 

 and mysteriously reappearing. Its distribution is very 

 limited, its headquarters being Kent, Surrey, Berks, 

 Bucks, Norfolk, north-east Yorks, Westmoreland, 

 Kings County, and County Down. The Involute Snail 

 {A. involida) is remarkable as being found only in 

 one station, a small tarn on Cromaglaun Mountain, 

 in County Kerry. It resembles a gliUinosa, in which, 

 by the growth of the body-whorl and that next to it, 

 the brief spire is almost hidden in a hollow at the top 

 of the shell. Owing to its remote habitat the animal 

 is not well known. The present writer has not seen 

 it alive ; but some writers say that it agrees with 

 glutlnosa in the mantle expansions enveloping the 

 shell, whilst others declare that the mantle is entirely 

 contained within the shell. It has therefore been 

 variously included as nearly allied to A. glutinosa, 

 and as being a unique variety of L. 'peregra ! We 

 note that Canon Norman in his Revision of the British 

 Molhisca sets it do^^'n as an Amphvpeplea, and we 

 therefore retain it as in his list. 



The next section of these Pond-snails comprises 

 the Flat-coils (Planorhis), made familiar by the 



