156 JOURNAL OF CONCHOLOGY, VOL. 9, NO. 5, JANUARY, 1S99. 



On one excursion of some of the members of our society, it is 

 recorded that upwards of 3,000 specimens of Vertigo were collected 

 in one day in one limestone quarry near Clitheroe, and in one garden 

 in Hampshire 1,591 Helix aspersa were killed in four nights. The 

 abundance of the amphibious Limncea peregra in every pond and 

 muddy hole, and of Helix rotundata in every sheltered spot, is well 

 known to all conchologists. The rate of increase of Agriolimax 

 agrestis is enormous, as a single pair have been known to lay 800 eggs. 

 These facts, then, taken in conjunction with the Distribution Tables 

 of the Referees of our Society, will, I think, give some idea of the 

 general abundance of our mollusca all over the country, and as their 

 food consists to a great extent of decaying animal and vegetable 

 matter, no doubt can remain as to the amount of useful scavenging 

 these animals perform. Another well known fact is that the decaying 

 vegetable rubbish heaps and heaps of wayside hedge and bank crop- 

 pings are irresistibly attractive to many of our molluscs, and form 

 some of their chief feeding-grounds, being in close proximity to their 

 retreats in the dense bottoms of hedgerows and thickets ; and thus 

 our country roads are to a great extent kept in a sanitary and whole- 

 some state. Again, in neglected arable and fallow land, so frequently 

 covered by a mass of weeds, especially of the coltsfoot, which in wet 

 autumn weather quickly decay, we see these fields cleared of this 

 unhealthy mass as well as of decaying fungi by our slugs and snails. 

 To show the pertinacity of Avion ater in clearing away decaying animal 

 matter, I have seen several of these molluscs crossing a pond by means 

 of the floating vegetation to reach a putrefying mass in the water. 

 t Then we find every nook and cranny in our old walls to be the 

 abode of some mollusc during the daytime, which sallies forth at dusk 

 to clear these walls and their surroundings from decaying matter. 

 Many of our most noxious garden weeds also form part of the food 

 of some of our molluscs, and so are kept in check to some extent by 

 them. Our large slug, Limax maximus, is a most useful dweller in 

 our cellars and drains, where by feeding on the accumulated greasy 

 and fatty matter adhering to the insides of pipes, where no other liv- 

 ing animal can penetrate, it assists in keeping drains open and free to 

 ventilation. One of our members, the Rev. J. W. Horsley, shows the 

 value of another mollusc {Hyalinia cell aria) in the following note con- 

 tributed to our Journal (July, 1898) : — " The other day a drain in my 

 area being blocked, I found it necessary to open the ground in the 

 forecourt, and in so doing found an unexpected man-hole covered with 

 slabs of stone. When these were lifted, I found four fine specimens 

 of Hyalinia cellaria on the under-surface of the stone where they must 

 have lived always in the dark and exclusively on what a scullery pipe 

 brought down. Walworth is in the densest part of South London, 



