46 BltlTISH MOLLUSKS. 



colour. Mr. Shuttleworth refers tlie Epistylia group of Helices in- 

 habiting Jamaica to this genus ; and Messrs. Adams refer some 

 forty or fifty foreign Helices to the genus. 



The British Zonites are eight in number, three of moderate size 

 and five much smaller ; the shells vary in being more or less glossy 

 with no perceptible epidermis, and the variation in size of the um- 

 bilicus, according as the whorls are more or less closely coiled, is 

 an obvious specific character. All the species inhabit wet and 

 sheltered situations, chiefly damp cellars, in preference to dry and 

 exposed places ; and as the animal has less need of enclosing the 

 aperture of its shell with any calcareous covering, the diaphragm is 

 reduced to a few filaments. According to Mr. Jeffreys, they greedily 

 devour animal food whether fresh or putrid. It is certain they are 

 often found in places where there is no sort of vegetation beyond fun- 

 guses. The only British Zonites not observed on the Continent is 

 Z. excavatus ; it may have been passed over as a largely umbili- 

 cated variety of Z. nitidus, but there are good reasons for keeping 

 it distinct. Two species, Z. cellarius and radiatulus, are included 

 in the fauna of the United States, having been transported acci- 

 dentally from Europe in casks or other packages, and become natu- 

 ralized there. 



The British species of Zonites are : — 



1. cellarius. Shell comparatively large, rather narrowly umbi- 



licated, pale glossy, spire convexly flattened. 



2. alliaria. Shell smaller, narrowly umbilicated, transparent 



horny, inclined to glassy, spire slightly convex. 



3. nitidulus. Shell rather larger than alliaria, but not quite so 



large as cellarius, more openly umbilicated, rufous above, 

 dull opake yellowish beneath. 



4. purus. Shell very small, rather largely umbilicated, greenish 



glassy. 



5. radiatulus. Shell very small, moderately umbilicated, greenish 



glassy, obviously radiately striated. 



6. nitidus. Shell much larger than purus and radiatulus, smaller 



than alliaria, rather largely umbilicated, brownish fulvous, 

 shining. 



7. excavatus. Shell rather larger than nitidus, often smaller, 



conspicuously excavately umbilicated, fulvous horny. 



