164 



OBSERVATIONS ON THE ANATOMY OF HELICELLA 

 " HERIPENSIS Mabille." 



By a. E. boycott and J. WILFRID JACKSON. 



(Read before the Society, November 12th, 1913). 



The specimens on which the following anatomical observations have 

 been made were collected during September last at Prestatyn, North 

 Wales, by Mr. R. Standen and one of the present writers (J. W. J.), 

 and besides being a new record for Flintshire (v.c. 51), they are also 

 the first specimens to be recorded for North Wales generally, and the 

 locality is the most north-westerly one known for the species. The 

 reference ^' H. caperata var. heripensis" in Mr. J. F. Musham's paper 

 on the 'Land and Freshwater MoUusca of lona' {antea p. 60) is a 

 mistake, the specimen in question being a malformed juvenile H. 

 itala, according to Mr. A. W. Stelfox. 



The species was found to be fairly common in several places on 

 the hedge-banks around Prestatyn, from the shore to the foot of the 

 steep limestone hills behind the town, and was accompanied in every 

 case by its ally, H. caperata. Its extreme abundance, however, was 

 more particularly noticeable (especially after rain) in an enclosed 

 stretch of marsh-land behind a line of old sand-dunes on the left of 

 the road (Bastion Road) leading down from the station to the shore, 

 and here it was associated with almost equal numbers of H. caperata, 

 and a fair sprinkling of H. virgata var. lutescens. All the shells of 

 this latter species were remarkable for their small size, while those of 

 both the other species were fairly large. 



The specimens upon which our observations have been made were 

 all taken from this area, and almost all the shells were found on the 

 ground, only a few occurring on the wall bounding the field. 



The habitat, about 15 feet above sea-level, is only scantily covered 

 with grass which is closely nibbled by sheep ; in places the sandy soil 

 overlying the marsh-clay is plainly visible between the grassy patches. 



Neither here, nor anywhere around Prestatyn, does there appear to 

 be any evidence of special plant associations having any influence on 

 the distribution and welfare of this species. 



In collecting we experienced no difficulty in distinguishing caperata 

 and " heripensis" as apart from differences in shell-sculpture and 

 ornament, the bodies, in general, of the ^'heripensis" were notably darker 

 than the caperata, though a few of the latter were darker than the 

 palest of the former and vice-versa. The pigmentation of the mantle- 

 edge was also different : in ^' heripensts" there was an obvious, almost 



