32O THE NATURAL HISTORY 



common during the summer and autumn months, on 

 the trunks of the beech trees in the park, and at other 

 seasons under stones, moss, and fragments of wood in 

 the surrounding covers, but when very young it often 

 escapes notice as a shell. The following extract from 

 a paper by the Rev d - Mr. Sheppard, in the Linnaean 

 Transactions (No. 16,166), will explain why: "These 

 shells, particularly in their young state, shew great 

 sagacity and ingenuity, by covering themselves with 

 a coat adapted to the different situations in which 

 they are found, and when so covered, it is almost 

 impossible for any other than a conchological eye to 

 discover them. If its abode be on the trunk of a tree 

 covered with lichen, then is the epidermis so con- 

 structed as to cause the shell to resemble a little knot 

 on the bark of the tree covered with such substance. 

 If on a smooth tree, from whose bark issue small 

 sessile buds, as is frequently the case, it will pass off 

 very well for one of them, and on a dry bank or the 

 lower part of the body of a tree splashed with mud, 

 its appearance will be that of a misshaped pointed 

 piece of dirt." Of course when the shell is fully 

 developed, this disguise is less perfect, although the 

 coating of extraneous matter is still conspicuous. The 

 Common Varnished Shell (Zua lubrica), a very glossy 

 little oblong shell of various shades of brown, is fre- 

 quent in the same habitats as the last. The Glossy 

 Trident Shell (Azeca tridens) we have found in com- 

 pany with the Zua lubrica, but one specimen only is 

 all that we possess of this rare species, a few others, 

 however, have occasionally been met with in the 

 warren. The Umbilicated Chrysalis Shell (Pnpa 

 ^lmbil^catd}, the Margined Chrysalis Shell (Pupa 

 Muscortim], the Toothless Whorl Shell ( Vertigo 

 edentula], and the Pigmy Whorl Shell ( Vertigo 

 pygm&a), all very minute shells, are found among 

 stones, chalk and moss, on old walls and tiled roofs 

 of old buildings in the park and elsewhere. The 



