AND THEIR INHABITANTS. 219 



long time without nourishment. Ancylus fluviatilis 

 (Miiller) has a dark slate-coloured body, with black 

 specks ; tentacles triangular at the base, eyes distinct, 

 but not prominent. The shell is semi-oval, incurved 

 like a helmet, the epidermis is thin. The shell is 

 not glossy, the spire forms the beak, and is equal to 

 about half a whorl. The length is 0-3 ; the breadth, 

 0*233. There are varieties, some larger, some smaller. 

 It is found on stones from Aberdeenshire to the 

 Channel Isles. A. lacustris (Linne) has a yellowish- 

 gray body, with a greenish tinge. The epidermis 

 is thick, and the beak sharp and ridge-like. The 

 length is 0*25, the breadth, o f i. Another variety is 

 compressed, and is much larger and flatter than the 

 type; one is milk-white, with a gray epidermis. This 

 Ancylus is found on the under leaves of water-lilies, 

 and other aquatic plants, as far north as Aberdeen- 

 shire. It has been taken in Staffordshire, and in 

 the Grand Canal, Dublin. It is easily distinguished 

 from A. fluviatilis by its habitat and the oblong 

 shape of its shell. Succinea amphibia, Pfeifferi and 

 oblonga, are little marsh-living animals whose shells 

 are of a beautiful transparent amber colour ; of nearly 

 similar habits is Vitrina pellucida. 



