348 JOURNAL OF CONCHOLOGY, VOL. I3, NO. II, JULY, I9I2. 



Coles' attention was drawn to the distinction between the two forms 

 and he very kindly sent the whole of the specimens collected. Of 

 these more than two-thirds were H. caperata, presumably, therefore, 

 the dominant. 



§ 3. Nature of habitat. 



Occurring as it does so frequently, but not by any means invariably, 

 with Helicella caperata it would seem that though the conditions of 

 life required by both species are in the main similar, there must be 

 other factors to take into account. My observations would seem to 

 prove clearly that first Helicella heripensis is strongly calcophilic, as in 

 every case in which I have met with the species it has been on a cal- 

 careous soil. In Sussex and Hampshire it occurs on the chalk of the 

 South Downs. In Leicestershire we find it on the Lincolnshire Lime- 

 stone (Inf Oolite) and in Northamptonshire and Huntingdonshire on 

 the limestones of the Upper Oolite. Moreover a careful consideration 

 of the localities enumerated by Mr. Stelfox certainly shows up the 

 the same fact. 



Again H. heripensis is certainly a xerophile, occurring always on 

 DRY calcareous pastures. At Barnack I found many one day quite 

 active, crawling on a limestone wall, with southern aspect, in the full 

 sunshine of a hot September day. It is probably as little or less 

 affected by drought even than the allied species of Helicella. 



Again, whether the plant associations supply any determining factor 

 I am unable to say. At Ufford there is nothing to the eye remark- 

 able in the habitat, yet curiously enough it is the locality for the 

 rather rare butterfly Arge galatea Linn., which is exceedingly plentiful 

 in this one spot, but seldom found elsewhere in the district. The food- 

 plant of Ai-ge galatea is the Timothy Grass, Phleum pratense, a very 

 common grass on dry soils. This spot is also the habitat of a some- 

 what rare plant, the Pasque-flower, Ane?fione Pulsatilla, a species 

 given to growing on dry uplands. 



To sum up, I believe a dry calcareous pasture, not necessarily 

 maritime, and at any ordinary altitude is the habitat most congenial 

 to Helicella heripefisis. I do not think it can be described as a 

 "strong" species, as it seldom seems to be the dominant. It is 

 closely allied in nature and mode of life to its near relative in the 

 Candidiila group, H. caperata, which, however, is a much stronger 

 competitor in the struggle for associated life than H. heripensis and 

 probably crowds it out in many places otherwise well suited for its 

 existence. 



The following analysis will show some of the facts as to association 

 with the other moUusca, as evidenced by the records given above. 



