FAMILY COLIMACEA. 53 



self at a height of about seven thousand feet, on the G-orner glacier 

 in Switzerland. The circumstance is interesting, from the fact of 

 this species having been for many years regarded as peculiar to 

 Britain; as a solitary instance of a British land snail, not inhabiting 

 the Continent. It now appears beyond all doubt that the British 

 Isles have no land mollusk of their own of any kind ; wherever the 

 origin of a species has been attributed to Britain, its history has been 

 surrounded with doubt and ultimately shown to be incorrect. 



8. Zonites crystallinus. Crystalline Zonites. 



Shell ; narrowly deeply umbilicated, subglobosely discoid, shining 

 opal homy, spire rather depressed, suture linearly _^ 

 channelled, whorls from four to four and a half, 

 rounded, finely striated, striae minutely plicated at .^fSs*^ 

 the suture ; aperture obliquely lunar-rounded. - ->r? 



Helix erystallina, Muller (1774), Verm. Hist. yol. ii. p. 23. 

 Helix ehurnea, Hartmann (1821), Neue Alp. vol. i. p. 234. 

 Helix vitrea, Brown (1827), Edin. Jowrn. vol. i. pi. i. f. 12 to 14. 

 Discus crystallinus, Fitzinger (1833), Syst. Verzeichn. p. 99. 

 Helicella erystallina, Beck (1837), Ind. Moll. p. 7. 

 Polita erystallina, Held (1837), Isis, p. 916. 

 Helix hydatina, Rossmassler (1838), Icon. Land mid Suss. Moll. p. 36. 



f. 529. 

 Zonites crystallinus, Gray (1840), Ttirt. Man. p. 176. pi. iv. f. 42. 

 Zonites ( Aplo stoma) crystallinus, Moquin-Tandon (1855), vol. ii. p. 89. 



pi. ix. f. 26 to 29. 

 Hab. Europe. Throughout Britain (under stones and among moss). 



The animal of this universally distributed species, the smallest of 

 the genus, is milk-white, and the shell always retains a shining 

 greenish crystalline or opal-like appearance. The whorls, which are 

 from four to four and a half in number, are convoluted, rather closely 

 and almost discoidly upon one another, the umbilicus being con- 

 tracted almost to a puncture. They are extremely regular, and the 

 delicate stria? with which they are scidptured are minutely puckered 

 in the suture. Zonites crystallinus occurs among moss and dead 

 leaves, under stones and upon decaying wood, both in dry and wet 

 situations, but more frequently in the latter. M. Bouchard-Chan- 

 tereaux remarks, that it is particularly common among plants in very 

 wet places upon the banks of rivers. 



