PLANORBIS. 91 



This is in all probability the Helix i:tlanorhis of the 

 ^ Fauna Suecica/ which is described as " plana" and 

 " margine prominulo;" but as the description and figure 

 given by Lister^ to which Linne there refers, sipply to the 

 Helix complanata of the latter, more confusion will be 

 avoided by the adoption of Miiller^s name. 



9. P. complana'tus "^^ Linne. 



Helix complanata, Linn. Syst. Nat. ed. x. p. 769. P. marginatus, F. & H. 

 iv. p. 165, pi. cxxvii. f. 1-3. 



Body of a deep violet-red, with very fine black specks, espe- 

 cially on the edges of the foot : tentacles very long and slender, 

 bluntly pointed : foot rounded in front, convex behind, and 

 ending in an obtuse tail. 



Shell concave above and slightly convex below, rather 

 soHd and opaque, not glossy, yellowish-horncolour with some- 

 times a tinge of brown, closely but irregularly striate in the 

 line of growth and more or less distinctly striate in a spiral 

 direction : epidermis rather thick : 'periphery strongly keeled 

 on the under side : ivhorls 6, the diameter of the last being 

 about one-fourth of the whole spire, convex above and slightly 

 so beneath, sloping abruptly on the upper, and gradually on 

 the lower side to the peripher}^ : suture moderately deep : 

 mouth roundish-oval, slightly angulated above by the keel, the 

 inside being sometimes strengthened by a rib : outer lip a little 

 reflected : inner lip continuous with it and affixed throughout 

 to the columella : umbilicus broad and very shallow. L. 0-125. 

 B. 0-6. 



Yar. 1. rhomhea. Shell smaller, more soHd, rather more 

 convex above and deeply umbihcated below ; keel blunt and 

 almost obsolete. Helix rhomhea, Turton, Conch. Diet. p. 47. 



Var. 2. alhida. Shell whitish or colourless. 



Habitat : Marshes, ponds, canals, ditches and stand- 

 ing water everywhere in England, Wales, and Ireland ; 

 but I am not aware of any Scotch locality. It is one of 

 our upper tertiary fossils. The variety 1. is from Dublin 



* Flattened. ' 



