COOKE : THE HABITAT OF GLAVSILIjE. 145 



little Bosnian maidens, who, in return for sundry coin of the realm, 

 turned themselves into ardent naturalists, I had amassed 179 specimens 

 of the fine CI. Bosnensis, Zieg., from this single dry limestone crag, 

 the face of which measured perhaps 12 yards by 3. 



This brings me to my final point. I feel quite certain that the 

 food of many species of Clausilia, and I think it probable that 

 I might add of Pupa and of Pomatias, is not green herbs of any kind. 

 I believe that they devour the surface of the limestone on which they 

 live. If we rub the limestone with our finger something ' comes off,' 

 and leaves a mark. I believe this is what Clausilia devours, for 

 I have frequently seen them living in spots where no green thing was 

 accessible, and I have good reason for believing that normally they 

 feed every day. Probably some minute organisms — of what nature 

 I do not here discuss — live on the disintegrated surface of the lime- 

 stone, and it is on these that the animals feed. Further, I believe 

 that they do so, not by selecting the organisms themselves, but by 

 swallowing the soft surface of the limestone whole, after rasping it 

 off with their radulse. In the case of CI. Almissana, noticed above 

 as preferring to live on bare limestone cliffs where there was a trickle 

 of water, the food is probably minute water organisms, devoured in 

 a similar way. And in confirmation of this view I may be permitted 

 to refer to an article in the Journal of Malacology^ vol. xii, 

 pp. 74-5, in which I advanced the theory, based upon a chemical 

 examination of the excreta, together with a consideration of its life- 

 habits, that Helix desertorum nourishes itself by swallowing large 

 quantities of sand, on which minute gelatinous organisms {JVbstoc 

 and the like) find a home. 



