Al.KlNS : TWO MOLLUSCAN ASSOCIATIONS IN NORTH-EAST STAFFS. 293 



relatively speaking only recently spread from the limestone on to 

 the newer rocks around. Thus we have here all the geological con- 

 ditions which can be desired to enable us to study the distribution 

 of the species. 



The occurrence of the two species separately and in association 

 will be detailed first for stations on the limestone and then for non- 

 limestone localities, coming in each case from north to south. 

 On the Carboniferous Limestone. 



1. Manor Farm Gorge, near Welton, Manifold Valley. On the 

 steep, arid slopes of Wetton Hill H. nemoralis occurs abundantly ; 

 the predominating form is of a rich deep purple-brown colour, and 

 comes near the variety olivacea Risso, as figured in vol. 3 of Taylor's 

 " Monograph," pi. 26; other forms are vars. libellula, rubella and 

 albolabiate albi/ia (two specimens) ; none of the shells seen possessed 

 a single band. ff. hortensis appears to be absent. 



2. Thor's Cave, Manifold Valley. At the foot of the limestone 

 cliffs on the west side of the valley both species occur in considerable 

 numbers, and in roughly equal proportions. The H. nemoralis are 

 bandless vars. rtibella and libellula (the purple variety mentioned 

 above is not present ; it appears to frequent drier and more exposed 

 situations), while the H. hortensis are typical or bandless. 



3. Bunster Hill, Dovedale. Both species are found in abundance, 

 and again in more or less equal numbers. If. nemoralis is again 

 bandless, and belongs to the var. libellula or, as is much more fre- 

 quently found, to the form so common in the Manor Farm Gorge. 

 The H. hortensis dx& occasionally bandless, but most often five-banded, 

 with little tendency to the coalescence of any bands ; it is noteworthy 



that the second band is often very feebly developed. 



4 and 5. At Cauldon and at Calton Moor H. nemoralis occurs 

 very sparsely ; vars. libellula and rubella are found. The Cauldon 

 specimens, one or two of which have the band formula 00300, are the 

 only ones taken by the writer on limestone in the county which 

 possess bands. H. hortensis has not been found in either locality. 

 The general appearance of the series of shells from each place is 

 intermediate between that of a typical limestone and that of a typical 

 non-limestone assemblage. 



6. Ramsor Quarry, Weaver Hills. Again both species occur — 

 accompanied here by H. arbustorutn ; the numbers of H. nemoralis 

 and H. hoilemis are again fairly equal. Of the former vars. rubella 

 and libellula, all bandless, and of the latter typical specimens, with 

 some coalescence of the bands, and bandless forms are found. 



Thus on the limestone, of four localities in which these species are 



S 



