TAYLOR: ON HELIX ARBUSTORUM. 253 



nettles, and Mr. Thompson states that it occurs at Knockdolian, 

 Ayrshire, with little more than '¥exr\'s, ( Cyslcsa fragilis ) to shelter it. 



Geology. 



This species can accommodate itself to different elevations 

 and to soil which yields very little calcareous matter, as granite 

 and gneiss. The extreme form which altitude and deficiency of 

 calcic element produces is found in the var. Bay lei from Mont 

 Dore. France, which is similar in texture to a Vitrhia. 



The opposite extreme would appear to be the var. calcarea of 

 Hoeberg, but I am without information as to the peculiarity of 

 its habitat. 



Mr. Borrer notes that it is found on bushy banks about 

 Henfield, Sussex, and other places on the sand, and is not found 

 on the clay. Mr. Christy has taken it in gravel pits, at Fulford, 

 near York. 



Dr. F. Buchanan White remarks that in Glen Tilt, Perthshire, 

 "it is in profusion on the limestone slopes south of the stream, but 

 not found at all on the gneiss to the north of it." 



Of 61 Yorkshire localities, 38 are situated on limestone 

 formations; 3 on the coal measures, but on the edge and near 

 limestone; 17 on the post tertiary; i on the trias; and 2 on the 

 drift. 



"Around Bristol the shells are very dark, perhaps from the 

 red soil, for although round Bristol Lias abounds, the Mountain 

 Limestone at Clifton seems preferred. I have noticed that in 

 chalky districts the white variety is more abundant, and the shells 

 are generally of a thinner texture, and the animals lighter in 

 color than ours here at Bristol, which are almost black" (Miss 

 Hele). 



Geographical Distribution. 



Pfeiffer gives as habitats, Germany, France, England, Sweden, 

 Podolia, Switzerland and N. Italy. 



