39 



THE OCCUEKENCE OF HELICELLA HEBIPENSIS (MABILLE) 

 IN GREAT BEITAm. 



13 y A. W. SxKLKox. 



Read 12th January, 1912. 



PLATE II. 



In the mouth of Octoher, 1907, when collecting in the neighbourhood 

 of Canterbury, I found a shell which appeared to me to be distinct 

 from any known British species. It was evident from the first that 

 it belonged to the group of Helicella caperata (Mont.), and most 

 collectors to whom I showed specimens were inclined to consider them 

 as a variety of that common species. Some examples were sent by 

 Mr. A. S. Kennard to the late Professor Boettger, who pronounced 

 them to be Helicella Ileripensis (Mab.),' but that in his opinion this 

 was not sjiecifically distinct from H. caperata (Mont.). Since 1907 

 1 have collected this shell many times in the southern counties, and 

 have observed no trace of an intermediate form between 11. Ileripensis 

 and S. caperata, although they live frequently in close proximity to 

 each other. Though it is with great diffidence that I venture to 

 differ from Dr. Boettger, I do not think we can do otherwise than 

 regard S. Ileripensis as a good species. 



In case the accompanying illustrations are not sufficient to permit 

 of the separation of the two shells mentioned above, I give below 

 what appears to me to be tlie chief distinguishing characters of 

 each, though it is a much easier matter to observe these in actual 

 specimens than to describe them on paper. 



Helicfxla capkrata (Montagu). Helicella Heripensis (Mabille). 

 (Figs. 12-17.) (Figs. 1-11.) 



GENERAL COLOURING. 



Varies greatly in colour from Usually of a creamy - brown 



pure white to almost black. colour, but often pale cream, 



Avith radiating markings. 



Monta<>u's type has a dark band The bands above the periphery 



above the periphery, visible on are always more or less inter- 

 all the whorls, while " at the rupted and faint, and never as 

 base of the shell are generally dark nor as distinct as in cer- 

 several small circular bands ; these tain forms of H. caperata. Bands 

 are frequently interrupted or beneath, numerous, seldom inter- 

 broken, and appear spotted". rupted, and frequently darkening 



near the lip, and then ceasing 



abruptly. 



1 Bull. See. Zool. France, 1877, p. 304. 



