3 I o Shell Life 



is about a tliird of an inch in length. The animal 

 feeds upon the minute vegetable growths that cover 

 the stones, and is especially fond of the aquatic 

 moss, Fontinalis antipyretica. It does not restrict 

 itself to the stream, but may often be found on 

 the wet mossy rocks above. The stomach is said 

 often to contain fine particles of sand, which are 

 thought to be taken to aid digestion much as fowls 

 fill their gizzards with gravel. It has been detected 

 in the act of getting a free passage to fresh streams 

 and waters new by clinging to the water-beetle 

 Acilius sulcatus, which uses its wings for a similar 

 purpose. The subjoined figure will give an idea 

 of the character of the teeth in this species. There 



Part of a row of teeth from the radula of Fresh-water Limpet 



are 120 rows, and cacli row contains a central tooth 

 and 37 lateral teeth on each side of it — a total 

 of 9000. The Fresh-water Limpet is generally 

 distributed throughout these islands. Its eggs are 

 deposited in little oval capsules, each containing 

 eight or ten. 



The Lake Limpet (A. lacustris) is a somewhat 

 smaller and more local species, with a more oblong 

 shell, the spire of which is distinctly twisted to the 

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

 inhabits lakes, ponds, canals, and slow rivers, adher- 

 ing to the under-side of floating and submerged 

 leaves of water-plants. 



The genus Ancylus is included in the family 



