280 HELICID.E. 



Combe near Bristol^ and Connemara (J. G. J.). Var. 5. 

 Northumberland and Durham (Alder) ; Oxfordshire 

 (Whiteaves). Var. 6. Sevenoaks, Kent (Smith). This 

 species occurs in our upper tertiaries. Its Continental 

 range extends from Finland to Portugal and Lombardy. 



The shells of different individuals of this species vary 

 considerably in the length of the spire and their com- 

 parative solidity, as well as in the degree of sculpture. 

 Sometimes a great part of the surface is quite smooth, 

 as if filed and polished ; and this is the case with living 

 specimens. How this effect is produced it is not easy 

 to say. Perhaps they lived in a sandy soil, and the 

 continual friction of the shells, when trailed along by 

 the animal, might account for the abrasion. Such spe- 

 cimens were in the collection of Dr. Turton and were 

 considered by him (as well as at one time by myself) to 

 be the C. parvula of Studer ; but the smooth and sleek 

 appearance of the last-mentioned shell is very diflPerent 

 from that of the above specimens. Some curious mon- 

 strosities occur, in some of which the spire is distorted, 

 or a faint keel or impressed lines encircle the whorls, 

 or the mouth is renewed in such a way as to show the 

 columellar folds in their incipient state. Lister was the 

 first to notice this shell ; and his communication to the 

 Royal Society ^^On the odd turn of some Shell-snails^^ 

 is one of the earliest on their records. 



It is (partly) the Helix perversa of Miiller, Turbo 

 bidens of Montagu (but not of Linne), T. nigricans of 

 Maton and Rackett, and Clausilia obtusa of C. Pfeiffer. 

 Many other names have been given by Continental au- 

 thors to difi'erent forms of this extremely variable species. 



C parvula differs from the present species in being 

 smaller and quite smooth, with the exception of some 

 very faint transverse lines, which are only observable 



