176 PNEUMONOBRANCHIATA. 



Inhab. under decayed wood, and timber that has 

 lain some time on the ground. 



Animal lead-coloured. 



Shell about one quarter of an inch in diameter ; 

 it very much resembles Z. lucida, but may be dis- 

 tinguished from it by its greater convexity both above 

 and below, and by its peculiarly large umbilicus; the 

 whorls are also rather more convex and more closely 

 set, and the outer whorl is not so large in proportion 

 to the rest ; the striae are rather stronger, the animal 

 lighter coloured, and it frequents a different situation. 

 The Shell varies in being paler. 



55. 12. Zonites crystallinus. Crystalline Snail, 

 (t. 4. f. 42.) Shell flat, glossy, of a greenish 

 crystalline transparency, with six very gradually 

 increasing volutions ; aperture semilunate ; um- 

 bilicus small. 

 Helix vitrea. Brown. 



crystallina. Drap. p. 118. t. 8. f. 13 —18. 



Gray] Med. Rep. 1821. 239.; Alder, Cat. 108.: 

 Turton, Man. ed. 1. 58. f. 42. ; Jeffreys, Linn. 

 Trans, xiii. 341. 511. 

 Zonites crystallina. Leach, Mollusc, p. 105. 

 Var. Helix hyalina. Ferus. Tab. Moll. 224. ? ; 



Alder, Cat. 108. 

 In wet meadows, among moss and leaves. 

 Animal milky white ; neck long, tentacles, dark 

 long, very active. 



Shell, when enclosing the animal, very shining 

 white, fulvous on the spire, hardly the eighth of an 

 inch in diameter, flat above and a little convex be- 

 neath, with six volutions, which enlarge gradually from 

 the centre ; of a crystalline or watery transparency 



