cviii. Proceedings. 



during his rambles. A few weeks since he had walked down 

 the valley from Caterham Junction to Caterham, and had 

 observed that along the roadside, near the Junction, Helix 

 virgata was the most abundant shell, with its variety alba ; 

 further along the road this species gave way to Helix cantiana, 

 which was the predominant species ; still further, both these 

 shells gave way to Cyclostoma elegans and Helix pomatia, so 

 that it would seem as if, even in a small district, there were, 

 so to speak, small areas affected by different species of 

 mollusca. He also exhibited and drew attention to some 

 remarkable forms of Limnea palustris which he had obtained 

 from the small pond at the foot of Croham Hurst on the 

 Croydon side. He observed that in almost every instance the 

 epidermis of these snails had been tunnelled through, in some 

 cases being entirely eroded. This, Mr. Lovett considered, 

 might possibly be due to a want of inorganic matter of a 

 calcareous nature in the water, and his experiments with some 

 of the living animals seemed to bear out this idea. The 

 channels in the shell were not at all like anything caused by 

 vegetable growth. He drew attention, in conclusion, to the 

 splendid series of local shells collected and exhibited by Mr. 

 McKean. 



Mr. Turner said he wished to ask Mr. McKean whether he 

 was to understand from his paper that Helix pomatia was 

 confined to the chalk district, for he had found it in great 

 numbers on the Cotswold Hills just about Cheltenham, and on 

 rocks of a calcareous nature elsewhere, although not to so 

 great an extent. 



Mr. McKean replied that he had taken the snail two miles 

 from the chalk escarpment, but not further. 



Mr. Turner said he was at Northampton in the spring, and 

 visited the secretary of the Microscopical Society there. He 

 showed him his aquarium, and told him that some time before 

 he had observed a young mussel, with which the aquarium was 

 well stocked, attached to the hind leg of a water beetle. He 

 wrote to Mr. Darwin, who thanked him for sending the obser- 

 vation to him, as it explained to him a circumstance he had 

 himself been puzzled about, namely, how bivalves could make 

 their way from one pond to another a considerable distance 

 away. This accounted for it. The water beetle was an animal 

 that did not remain in the water in which it lived, but in the 

 course of time got out and flew away, and in doing so carried 

 away with it anything that might happen to be attached to its 

 limbs. In this way Darwin considered the bivalves were carried 

 about from one place to another. This encouraged the observer 

 to make further observations, and see if he could find any 

 other circumstances of a like nature. He did so, and a short 



