BRITISH NON-MARINE MOLLUSC A. 



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extend for miles in various directions, especially along the 

 picturesque western escarpment, in many of the " combes, " and 

 frequently crest the higher ridges, constitute the habitat of 

 many " good things" which are very scarce or local elsewhere; 

 while the numerous parish commons, covered with their charac- 

 teristic grasses and aromatic herbage, afford a happy hunting- 

 ground for the heath-snails and other species which frequent 

 such situations. 



The whole district forcibly reminds one of the chain of the 

 Jura Mountains between France and Switzerland, where the 

 Jurassic system is so magnificently developed. Of these distant 

 mountains the Cotteswolds seem, as it were, a small detached 

 fragment, considering their similarity not only in the geology but 

 in the fauna and flora as well, though of course all existing here 

 are on a comparatively much inferior scale. In the extensive 

 beech forests of the Jura, the same as in the beech woods here, 

 one may meet with Ena montana and E. obscura climbing up the 

 smooth tree-trunks in company with Clausilia bidentata and 

 C. laminata, with its white variety albida, while upon the ground 

 the gigantic Helix pomatia is equally at home. 



Although the last-named species is found on the Continent 

 in a great variety of situations, such as upon grassy banks by 

 the roadside, and even in gardens remote from woods, in the 

 Cotteswolds it is apparently confined exclusively to the arboreal 

 areas, many yards from the beneficent shelter of which it seldom 

 strays, at least, according to my own observations. Here it 

 ascends to about 950 ft. above the sea-level — that is, to the 

 extreme upper limits of the arborescent vegetation — and would 

 no doubt continue to ascend for another two or three thousand 

 feet still if the wooded hills were of a sufficient elevation, as I 

 have seen it up to at least 5000 ft. in the Eastern Alps (in the 

 Canton of the Grisons), which is well within the Lower Alpine 

 or Pseudo-sub-Arctic zone, or belt of conifers. 



Kespecting the influence of altitude and environment upon 

 their morphology, it is interesting to note that there are two 

 extreme forms of the shell as regards coloration in the Cottes- 

 wolds. The first, which I distinguish as var. arbor ea (mihi), is 

 a dark one inhabiting the deep recesses of the woods between 

 400 ft. and 750 ft., where it is difficult to discern by reason of its 



