Tond-snails 309 



The Little Ear-sliell (Otlna otis) is like a copy in 

 minature of the shell of Velutina (see page 219), 

 but the animal is different. When gliding over the 

 little black lichen that grows abundantly over the 

 littoral rocks, its shell is evidently several sizes too 

 small to shelter it, but when the tide goes out, and 

 the lichen dries up, Otlna shrinks and contrives 

 to get efficient shelter. It is thin, and almost trans- 

 parent, some shade of red-brown tinged with purple. 

 Its measurement is only about one-tenth of an inch ; 

 so it requires to be carefully sought. 



We are now done with the seashore for a long 

 interval, but we may leave it in the pleasantest 

 manner possible, by way of one of the fresh-water 

 streams that come down the valley and get lost in 

 the sandy beach. Here, on the stones in the bed 

 of the stream, we shall find a tiny limpet-shaped 

 shell closely adhering in defiance of the strong 

 current of fresh water for ever rushing over it. 

 This is the Fresh-water 'Lim'pet (Aiicylus Jliiviatilis), 

 so-called in deference to the shape of the shell re- 

 gardless of the nature of the mollusk that made it. 

 The resemblance of the shell is to Helcion not 

 Patella, but the animal is widely different from 

 either of these species, and shows near relation to 

 the common Limna3ids of our ponds. It has a large 

 head with short cylindrical tentacles, 

 the eyes at their triangular bases. 

 The oval foot is almost as large as 

 the mouth of the shell. The thin 

 shell is yellowish grey, devoid of gloss, and covered 

 by a thin epidermis; the spire turned slightly to 

 the right, whilst the animal is twisted to the left. It 



