BEESTON : SINISTRAL LIMN^A GLABRA. I9I 



Sinistral Limnaea glabra. — In August last while staying at Scarborough in 

 company with another member of the Conchological Society I was fortunate enough 

 to discover a reversed specimen of this rather uncommon species. So far as I am 

 able to discover, no previous record of a sinistral L. glabra has ever been noted on 

 the British list, so that this discovery is quite unique. The specimen also belongs to the 

 monstrosity decoUatum. In connection with the find there are one or two points 

 worth noting which came under our observation at the time. The locality is a small 

 triangular piece of ground by the roadside, and to all appearances is nearly dry 

 throughout the summer, being supplied with water from the road drainage only after 

 rainfall. No doubt in winter the slight hollow would become filled with water, but 

 it was almost dry in August, except for a little dampness at the roots of the long 

 luxuriant grass. This marshy bit of ground is, according to good authority, the 

 only place where L. glabra is to be found in the vicinity of Scarborough and is thus 

 a rather favourite locality with local conchologists. I am indebted to Messrs. 

 Gyngell and Hargreaves of Scarborough for introducing me to the spot, and on one 

 or two previous occasions I have had the pleasure of collecting there with them. 

 An interesting point which is worth recording was the difficulty we both at first 

 experienced in finding a live specimen. We came across many shells with the top 

 whorls eaten entirely away, nothing but the first one being left, and in almost every 

 instance they were the largest and best shells. Investigation revealed the fact that 

 either mice, or possibly field voles, were the depredators, as the ground was literally 

 honeycombed in every direction with their burrows. We almost despaired of finding 

 a living shell, but after casually striking the tall grass with a stick we discovered one or 

 two specimens lying at the roots. After that, by beating the grass about a foot from 

 the ground, we were rewarded by finding a few more. Evidently the snails had left 

 the damp ground and climbed some distance up the grass stems, whence they were 

 dislodged by beating. Very few of the shells were full grown, the voles having been 

 before us and cleared out the adults. The shells were extremely clean and, when 

 the animals were taken out, required very little preparation for the cabinet. They 

 were very transparent and thin, quite unlike specimens I obtained during the month 

 while collecting in two other districts, viz., Manchester and Longton (Staffs.). The 

 Manchester specimens were rather dirty and covered with confervse, which was 

 removed easily with a stiff brush after boiling, but those from the Staffordshire 

 locality were black as ink, having a thick coating of what I take to be soot or 

 very hard black mud, and required scraping with a knife. They were taken from a 

 roadside ditch on the outskirts of Longton, and were most difficult to discover as 

 they were found adhering lengthwise to thin pieces of black decaying stick in the 

 shallow water. I ought to mention that the reversed L. glabra was, unfortunately, 

 only about two-thirds grown, but possibly under the care of the authorities of the 

 Manchester Museum the animal may arrive at maturity in the course of time. A 

 very large proportion of the shells of L. glabra from the Scarborough locality are 

 the decollate form, and the usual explanation that the apices are worn away by 

 attrition as the animals crawl about is not, in my opinion, a satisfactory one. It 

 seems much more likely that the animals themselves are the cause of the decollation ; 

 not finding sufficient shell-building material in their food, they have discovered that 

 their neighbours' shells supply suitable and convenient calcareous matter, and so at 

 a very early stage of their existence they begin to rasp off small particles, thus pro- 

 ducing the worn and incomplete appearance so noticeable. I once saw a number of 

 dead H. nemoralis shells which had been, and were being eaten in holes by H. 

 aspersa for the sake of the limy matter of the shells. Many water shells are often 

 seen damaged in this way and no doubt the cause is the same. — H. Beeston {Read 

 before I hd Society, November I3tb, 1907). 



