BRITISH NON-MARINE MOLLUSC A. 



49 



maugei, T. haliotidea, and T. scutulum, alien species which have 

 hitherto been recorded only, as far as I am cognizant, from 

 gardens in the Tale, between 50 ft. and 300 ft. above the sea- 

 level, where they were no doubt originally introduced with exotic 

 plants. Another class are confined exclusively to the middle 

 altitudes, apparently the presence of the woodland areas deciding 

 their occurrence in an affirmative way. Among these may be 

 enumerated the local Ena montana, Clausilia rolphii, and Hy- 

 gromia fusca, with, perhaps, Helicella cantiana, Azeca tridens, 

 Coecilioides acicula, and Succinea oblonga. As regards the first 

 named, Ena montana, this only occurs, according to my present 

 knowledge, in three different stations here, but will no doubt 

 be eventually found in others when looked for, as in one of 

 them, which I consider to be its metropolis in the Cotteswolds, 

 it occurs in considerable abundance. It is found exclusively in 

 the beech woods at not less than 400 ft. and never more than 

 750 ft. above the sea-level, according to my experience. I dis- 

 tinguish three forms with reference to coloration, viz. : (1) what 

 may be termed the typical form of a dark brown, fairly pellucid ; 

 (2) of a pale brown and semi-diaphanous, which I call var. 

 cottesivoldensis (mihi) ; and (3) of a pale opaque brown, the var. 

 birdlipensis (mihi). Although I have examined a considerable 

 number of specimens at different times, I have hitherto failed to 

 meet with the white aberration albida, which I have, however, 

 found in the commoner Ena obscura on several occasions. 



Concerning the local Clausilia rolphii, of which, by the way, I 

 have just recently discovered an additional locality (which makes 

 th ree places where it exists here to my present knowledge), I 

 distinguish two forms as regards colour — the first dark brown 

 and the second with a reddish tinge and somewhat pellucid. In 

 regard to size, they vary somewhat ; the more elongated forms I 

 call var. major (mihi), and the small stunted specimens var. 

 minor (mihi). The common C. bidentata also varies considerably 

 in size, the longest being confined to the woods, the shortest 

 being found principally on the higher ground and more exposed 

 places generally. 



Of C. laminata, I distinguish five different forms in the Cottes- 

 wolds. It is often an abundant species up to 950 ft. or so, 

 though in the more elevated and exposed places it assumes a 



