_Balea perversa_ (_i.e._ sinistral) is a much larger shell belonging to the Clausilia family. Thin, dark horn-colour, semi-transparent, glossy, 7 to 8 whorls, local, but abundant where found. Chiefly found on trees.
_Clausilia (Pirostoma) bidentata._--All our British clausilias are sinistral. The clausilium (little door) is an internal contrivance fastened to the pillar of the shell (whereas an operculum is attached to the body of a mollusc) by an elastic ligament to protect it against insect enemies when the animal withdraws. _Bidentata_ has two denticles, fusiform and reddish-brown, as are all. Very common on walls and trees.
_Clausilia (Pirostoma) rolphii._--Rare and local. Almost subterranean in habit. More coarsely striated than the last. The upper whorls nearly of the same breadth, forming a short cylinder.
_Clausilia (Alinda) biplicata._--Very local. Chiefly on Thames willows. Larger than the two former, and streaked with white.
_Clausilia (Marpessa) laminata._--Much like the former, but widely distributed. Usually found on beech and ash trees, and on limestone rocks. Smooth and glossy.
In the family Stenogyra we have three genera, Azeca, Cochlicopa, and Cæcilioides (with also the imported _Stenogyra Goodallii_, found only in pine-houses).
_Stenogyra (Azeca) tridens_ is a small chrysalis-shaped, solid but semi-transparent shell, horn-coloured, with 3 denticles. Not rare in moist places.
_Stenogyra (Cochlicopa) lubrica_ (_i.e._ slippery).--Very common in moss and under stones or logs. Much like the previous species, but no denticles and fewer whorls, and broader mouth.
_Stenogyra (Cæcilioides) acicula._--If this word is supposed to be Latin it would mean either "like to a blind worm" or "like to a lettuce"! _Cæcus_, however, being Latin for blind, the allusion is no doubt to the fact that this wholly subterranean species is eyeless. The only British representative of a large family of carnivorous molluscs. I have found it on Saxon bones when unearthed, and in crevices of limestone underground, but it is generally found dead amongst the rejectamenta on the banks of rivers. It is a pretty, glossy white shell, 5 millimetres in height by 1 in breadth.
I may notice here two other land shells, although they scientifically are grouped amongst the fluviatile Gasteropoda.