114 



97. PLANORBIS albus. Shell concave on both sides, 

 with fine raised hispid spiral striae. 



Planorbis albus. Leach, Mollusc. p. 156. 

 Planorbis hispidus. Drap. p. 43. t. l.jT. 45 48. 



Bmrd,p. 159. t. 6./. 6, 7. 



Helix alba. Mont. p. 459. t. 25. /. 7. 



Shell about a quarter of an inch in diameter, very 

 thin and brittle, pale horn-colour, marked with 

 very fine close-set raised circular striae, which are 

 clothed with deciduous bristles, and crossed with 

 obscure longitudinal lines : volutions five, the first 

 very large and rounded ; the upper surface a little 

 sunk in the middle, the under side more strongly 

 concave : aperture roundish-oval, dilated, higher 

 than wide, with the upper angle much produced. 



When quite fresh, this beautiful species is clothed 

 with a fine velvety pile composed of short points 

 seated on the raised concentric striae, and which fall 

 off with the epidermis ; and in its depilated state 

 may be the Helix SpirorUs of Linne, as he no 

 where also mentions so very common a species, 

 Gmelin having probably quoted it twice, both as 

 H. Spirorbis and H. alba. In this state it answers 

 well to his character of H. SpirorUs, in the Fauna 

 Suecica, " testa utrinque concava, plana, albida : 

 anfractibus quinque teretibus." 



