CHAPTER LXV: NORTH AMERICAN LAND 



SNAILS 



North American genera of the Helices may be grouped by 

 peculiarities of the lip of the shell into four classes. Certain 

 notable exotic genera will be mentioned with natives in their 

 proper class under this simple key, made by Dr. Pilsbry for 

 beginners. 



A. Shell with thin, sharp lip, not expanded: 



Genus Pyramidula , 



Genus Glyptostoma 



B. Shell with blunt, thick lip, not expanded: 



Genus Polygyrella 



C. Shell with lip expanded, not flatly reflexed: 



Genus Epiphragmophora 

 Genus Vallonia 



D. Shell with lip decidedly reflexed, often toothed: 



Genus Polygyra. 



THE PYRAMID SNAILS 



Genus PYRAMIDULA, Fitz. (PATULA of recent 



authors) 



Shell cone-shaped to flat disk-shaped, with open umbilicus; 

 opaque, one-coloured, banded or flame-streaked; whorls rounded 

 or keeled; aperture rounded; lip thin, simple. Foot undivided, 

 lateral margin with a border set off by a groove. No mucus foot 

 pore; eye peduncles long and slender. 



Dull coloured, ground-living snails, found all over northern 

 temperate land areas. 



The type, P. ruspestris, Drap., is a neat, low-coned, brown 

 snail with rounded coils and a deep pit. Diameter, h inch. 



Habiiat. — Central and Southern Europe. 



The Perspective Pyramid (P. perspectiva, Say) shows a 



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