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ANCYLUS FLUVIATILIS var. GIBBOSA Bourg. 

 IN DERBYSHIRE. 



By R. STANDEN. 



(Read before the Society, November 13th, 1912). 



A FEW white Ancyhis were taken in Dove Dale, in October, 1910, by 

 Mr. J. A. Hargreaves, of Scarborough. ■ On applying to him for 

 particulars respecting the exact locality, all the information he could 

 furnish was that he got them " amongst watercress." As both my 

 friend, Mr. J. Kidson Taylor, and I were desirous to take this variety 

 for our own collections from a Derbyshire locality, we determined, 

 whilst I was on a visit to him during October last, to have a thorough 

 search for it. Accordingly, taking an early train to Alsop-en-le-Dale, 

 we walked through Mill Dale, and on entering Dove Dale proceeded 

 along the river side until we came to a large watercress bed, which 

 filled up a narrow, rather deep runnel of spring water, issuing from 

 the mountain side, in close proximity to the River Dove, and about 

 midway between Mill Dale and the famous rock pinnacles known as 

 Tissington Spires. On tearing up and rolling back the thickly matted 

 watercress, the clean limestone fragments, partially filling up the 

 runnel, were seen to be covered with Ancylns, in all stages of growth, 

 but full-grown shells were decidedly scarce, and a long and careful 

 search was necessary to secure a decent set each. Both adult and 

 young had the swollen shell, with beak over-hanging the posterior 

 margin, which are the distinguishing characteristics of the variety 

 gibbosa, and it was the recognition of this form that induced us to 

 persevere in the endeavour to obtain a good set for ourselves and 

 friends, for they showed no signs of being the white variety of which 

 we were in quest, and otherwise we might have passed them by as of 

 little consequence. About a mile further down the Dale we came 

 across a very similar spring runnel, but in this case the outflow was 

 more widely spread and shallow, and the uppermost stones were 

 covered with a thick growth of Fontifialis antipyretica — a plant which 

 I have noticed associated with Aiicylns in many places. Here adult 

 shells, of exactly the same type as at the previous locality, were 

 abundant, whilst young individuals were scarce. In neither place 

 was it possible to ascertain whether the shells occurred in the river 

 itself, for it is rather deep and rapid at these points, but in all 

 probability they do. 



The shells, when seen on the stones, and also when gathered, 

 appeared to be intensely black. This black colour, however, is 

 entirely confined to the animal, and we were agreeably surprised, on 



