ANCYLUS. 71 



B. Body dextral ; shell sinistral. 

 2. A. lacus'tris,* Linn^. Pl. V. 



Body greenish-yellow, finely spotted with black ; tentacles 

 widely separated, thick, rather transparent, whitish-grey, tips 

 pointed ; eyes distinct, but not prominent, round, black ; foot 

 greenish-yellow, truncate in front, rounded, and of a somewhat 

 darker colour behind. 



Shell much more oblong in form than that of the last species, 

 and thinner, rather glossy, horn-colour, faintly tinged with 

 yellow or green ; strice as in A. fiuviatilis, but they are finer 

 and much less distinct ; epidertnis rather thick ; spire ridged, 

 apex acute, distinctly twisted to the left ; mouth oblong, inargin 

 membranous, somewhat reflected. 



Inhabits sluggish streams, lakes, and ponds, at- 

 tached to the under side of the leaves of aquatic 

 plants, especially those of the water-lily, in many 

 parts of Great Britain, but it is much more local than 

 A. fiuviatilis. This species adheres less firmly than 

 the last to the objects to which it attaches itself. It 

 seldom moves from place to place, but when it does 

 so it crawls somewhat rapidly. Moquin-Tandon says 

 it is rather difficult to count the number of its eggs 

 owing to their extretne transparency ; that they usually 

 number from four to twelve, are of an oval form, 

 and not crowded so closely together as those of the 

 last species. The capsules in which they are enclosed 

 are roundish, considerably compressed, transparent, 

 and covered with numerous minute tubercles. The 

 young are hatched in from twenty to twenty-six 

 days. 



* Living in lakes. 



