132 PEARCE : VARIETIES OF HANDED SNAILS. 



(i) Form with uniformly brown 

 shell, now represented perhaps by the variety fidva which is probably a 



reversion from No. 2 or No. 3. 



(2) Form in whicli jjaler shades | 

 appear on brown shell ' 



(3) Form in which pale and dark ■ Forms in which mottlings tend- 



shades or mottlings are equally ing to form bands, have been 



balanced- -(9;v/z'«a;j mottled form. perpetuated by sheep on pasture 



I lands — var. omata. 



(4) Form in which dark mott- 

 lings are fast disappearing. 



(5) Form with an uniformly pale Form in which the dark band or 

 whitish shell without any mottlings bands of var. omata are lost until 

 — var. albicmis. a shell similar to var. albicaus is 



arrived at. 



N.B. — Those rare forms in which the dark mottlings or banding are replaced 

 by transparent markings, may be explained by the failure of the animal 

 material, which is the basis of the dark colouring matter in the shell. 

 It is possible for any of the above forms to show translucent 

 characteristics . 



The evidence as to the proportion in which the varieties of 



H. caperata occur in the sheep pastures and in other locaHties, 



given only summarily in the body of this paper, we here append 



in detail. 



In September, 1887, on the chalk downs between Freshwater 



and the Needles Point, Isle of Wight, I gathered material which 



first suggested the fact that the variety ortiata was restricted 



to places where sheep pastured. From seven squares of three 



feet each, measured out, but at different points on the above 



downs, where sheep frequently pastured, I collected the two 



varieties of Helix caperata in the following proportions : — 



27 individuals of the var. omata, to 



14 ,, ,, ,, mottled form. 



Quite at the extremity of the down at the Needles Point, 



where the down surface has become rubbly and loose, and so 



is not suitable for sheep pasturing, the two varieties of Helix 



caperata occurred in an exactly reverse proportion : — 



4 individuals of the var. ornata, to 



14 ,, „ ,, mottled form. 



J.C., vi., Oct., i88q. 



