170 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



an occasional specimen of Clausilia hideniata may he found but, 

 otherwise it seems to avoid any companions except woodlice 

 [Porcellio scaher). It happens pretty often on these trees that, 

 owing to some injury or disease, a piece of bark has become so far 

 detached from the trunk that it has behind it a layer of brown 

 granular, often dampish, debris (? faeces of larvae), in which live 

 worms, lulus, and sometimes Pyrawidula rotundata and Hyalinia 

 alliaria ; in these more populous places perversa is not found, 

 though there may be plenty of them on other parts of the same tree. 



In winter worms climb up along the crevices in the bark more 

 freely, and may be found with 2^c-i'^^'>'sc(i which is exceptionally 

 indifferent to cold weather.^ 



Though its habitat on the trees is essentially a dry one, perversa 

 is, I think, found more freely on the south-west sides, which receive 

 most rain, and on the areas along which in a forking tree (e.g. aj)ple) 

 the rain runs down the trunk. The bark in these places is looser, 

 or, at any rate, more readily detachable : whether this or the rather 

 greater dampness is the reason for their preference I do not know. 



The relation of perversa to the trees must be clearly distinguished 

 from that of E7ia obscura, Clausilia laminata, CI. bidentata, 

 Liniaz arborum, etc. These anabatic species, as they might be 

 called, climb up trees freely in wet weather and may stop there 

 several days, but their home is on the ground, whereas perversa 

 lives up the tree all the time. 



Rocks and walls afford adequate habitats irrespective of their 

 nature so long as they furnish holes and crannies and are. not wet. 

 Very few live things except woodlice will be found there, and they 

 reproduce by entirely different means the characteristics outlined 

 for the suitable trees. There is, indeed, nothing common to the 

 different places excej)t dryness, absence of many other animals, and 

 remoteness from the ground. As far as I know, the species has no 

 relations with any plants : the authorities often mention moss, 

 lichens, etc., but these seem to have no importance beyond providing 

 shelter, for many of its homes are quite destitute of any vegetation 

 more elaborate than Protococcus. 



Balea is A^ery seldom found on the ground. I have notes of only 

 one definite and four probable records : "at the roots of decaying 

 herbage on the rocks of the [Plymouth] Hoe,"^ " among decaying 

 leaves on Walton Downs, near Clevedon,"^ " among decaying 

 wood and dead leaves, or lurking in moss,"^ " at the foot of trees, 

 concealed by grass,"^ " among moss and dead leaves, "° in Devon. 



^ A. W. Stelfox, Proc. Roy. Irish Acad., xxix (1911), 102 ; J. G. Jeffreys, 

 Brit. Conch., i, 274 ; C. M. Steenberg, Landsnegle, p. 151. 

 2 S. S. Bolton, Naturalist, iii, 1853, 128. 



=* A. M. Norman in E. W. Swanton, Mollusca of Somerset, 1912, v. 42. 

 4 R. Tate, L.F.W. Molluscs of Great Britain, 1886, p. 165. 

 ^ Coo]3er in J. E Harting, Rambles in searcJi of Shells, 1875, p. 64. 

 •> M. J. Longstaff, Journ. Conch., xiii, 107. 



