2o6 



UPPER NIDDERDALE AND ITS FAUNA. 



MOLLUSCA. 



The most striking characteristic of the molluscan fauna of Nidder- 

 dale, imperfectly studied as it has been, is the almost total absence 

 from it of freshwater species, the ubiquitous Limncea peregra being 

 the only one as yet recorded for the dale. Nor can we expect 

 more than, say, half a dozen species to be found, for the Nidderdale 

 area is one of rapid and impetuous streams, and hardly offers scope 

 anywhere for standing waters of sufficient permanence to attract many 

 species. Of land shells 32 species, and of slugs seven species have 

 been noted, and there are doubtless various forms still to reward 

 further investigation. Not that much variety of station is afforded 

 by the district generally, the almost uniform geological structure of 

 which does not tend to the nourishment of molluscan life, save 

 where the limited outcrops of mountain limestone at How Stean and 

 on Greenhow Hill impart a new element to the district, the effect of 

 which is seen in the presence of such species as Helix lapidda, 

 H. rupestris, Balea, and Clausilia lamtnata, all of which, as well 

 as other species, are in Nidderdale confined to the calcareous 

 element in the soil. The observations embodied iri the list which 

 follows are mainly the result of the investigations of Mr. Storey, 

 about Pateley, and of Mr. F. T. Walker, about Birstwith, and also 

 include scattered observations made by other naturalists. For the 

 determination of all Mr. Storey's and many of Mr. Walker's speci- 

 mens we have been indebted to Mr. J. W. Taylor. It may be added 

 that the list should include another species of slug, which, however, 

 has not yet been formally proclaimed as a member of the British 

 fauna, and is, therefore, for the present omitted. 

 Arion ater. Abundant throughout the dale, from 1,500 feet 



elevation on the slopes of Great Whernside downwards. 

 Arion hortensis. Birstwith, Ramsgill, Pateley, etc. Common in 



cultivated tracts. 



Amalia marginata. Has been reported as occurring at Pateley 



Bridge, but the record is open to grave doubt. 

 Limax maximus. Near Pateley Bridge and Goydon Pot ; very 



common at Birstwith. 

 Limax arborum. An abundant species in the dale ; has been noted 



at Pateley Bridge, near Gouthwaite, at Glasshouses, and near 



Ripley. 



Limax flavus. Rennie Crags, near Birstwith (F. T. Walker). 

 Limax agrestis and vars. sylvatica and tristis. Very abundant 



throughout the dale, from 1,200 feet elevation downwards. 

 Vitrina pellucida. Very common in damp woods ; Birstwith, 



Ripley, Pateley Bridge, Ramsgill, etc. 



Naturalist, 



