31 

 FIELD NOTES ON HELICODONTA OBVOLUTA Miiller. 



By H. BEESTON. 



(Read before the Society, February 14th, 1917). 



Since being domiciled in Hampshire, no shell has interested me more 

 than that very local and comparatively rare mollusc, Helicodonta obvo- 

 luta. Living within easy reach of its well-known habitat — Ditcham 

 Wood — and enjoying full liberty to explore it, I have had special 

 opportunities of observing, studying and collecting the shell in its 

 native haunts. It is not my purpose to describe either the animal or 

 the shell. I desire rather to discuss several aspects from the col- 

 lector's point of view. 



The species was discovered in this country in the year 1830 by 

 Dr. James Lindsay, who resided for some time in the district, and 

 recorded the discovery in the Linnean Transactions, xvi, p. 765. 

 It was unknown to Turton when he published his first edition of 

 " The Manual of Land and Freshwater Shells of the British Islands " 

 in June, 1831, but it appeared on plate xi of Gray's edition, issued 

 in 1840. 



I have no positive evidence when copulation takes place, but am 

 inclined to think it occurs in early spring — about April or May. 



Miss Hele's ^ observations accord very well with my own, as I more 

 frequently find very young specimens in June, July, and August 

 than during the earlier or later months. But I am of opinion that 

 eggs are laid successively all through the summer, as shells in all 

 stages of growth are to be found very late in the autumn, and occa- 

 sionally in winter, about one-third grown, with the mouth sealed with 

 a calcareous plate. Whether the eggs are laid in batches or singly I 

 am unable to say, but am inclined to think they are deposited either 

 singly or at most two or three at a time, as I have never been able 

 to discover more than one or two young ones together, and these 

 usually in various stages of development. In searching for the 

 species I have frequently found small white eggs, which I believe to 

 be those of H. obvoluta, among the dead beech leaves, and these cer- 

 tainly were not laid in clusters, as most of the larger Helices are 

 usually found. The young of H. obvohita are not gregarious ; and 

 if later observations should prove that eggs are laid in batches, then 

 the young quickly separate. 



Mr. L. Dawes' experience of breeding this snail in captivity differs 

 from mine. He writes as follows : — " The eggs are white, laid iti 

 clusters of from tivelve to twenty, mostly sixteen, the time of laying 



I Journ. of Conc/i., v, 8.^. 



