a 
426 HELICIGONA ARBUSTORUM. 
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In Scandinavia, it is recorded by Odhner from the post-glacial beds of 
Jamtland, Sweden ; and from those of Gudbrandsdalen, Norway. 
In Denmark, it is found in the submarine marshes, Freihavnen near 
Copenhagen, and in the freshwater limestone at Stovaflyning near Oxne- 
bjerg in Jutland. 
Variation.— /Teliciyona arbustorum is apparently only a conditionally 
dominant species, as is shown by its inhabiting and being more or less 
restricted to moist places in valleys and elsewhere and the more elevated 
hilly or mountainous regions, extending to and bordering upon the verge 
of perpetual snow, under which in some alpine and extreme northern 
districts they are usually buried for the greater part of their existence. 
From this wide difference in character and altitude and the strict localiza- 
tion of their colonies there naturally results a remarkable differentiation 
in the general aspect of the shells which has led to a considerable number 
of names being applied to the various modifications. 
The varieties of diminished or diminutive size with an elevated spire 
would seem to be more particularly characteristic of mountainous regions 
and the more northern localities, though also found in marshy districts 
and sporadically elsewhere, while those inhabiting the lower ground or 
more genial southern climes are usually of a larger and flatter type. 
In substance the variation is also considerable, some shells being strong 
and thick, while others are of excessive tenuity and indeed little more than 
a mere organic film; these results are usually assumed to be the outcome 
of living upon a calcareous soil or upon one deficient of that substance, 
but though this undoubtedly has a great effect, the difference is probably 
often physiological and due to the efficiency in the selective action of the 
tissues of the individual snail. 
The effect of food in influencing or modifying the colouring of the shell 
of this species has been frequently affirmed, the yellow varieties being 
observed by Mr. W. Baillie to be always more abundant and finer about 
plants of the meadow sweet (Spir@a ulmaria) and coltsfoot (Tussilago 
Jarfara), while amongst nettles the shells are generally darker in colour. 
‘The influence of the character of the food upon the colouring or pigmenta- 
tion of the shell is strikingly shown by the fact that some immature 
individuals of the var. fusca, found by Capt. Farrer at York feeding upon 
wild parsnip, were conveyed to Bassenthwaite and there fed to maturity 
on cabbage and lettuce, but the new growth of every shell was of the 
typical character or referable to the var. flavescens, and the junction of the 
new growth was thus very distinctly indicated. 
“Pink” shells are recorded by the late Mr. Sherriff Tye as found feeding 
upon coltsfoot at ‘“Wren’s Nest,’ Dudley, and the same variation was 
discovered by Mr. R. Wigglesworth at Clitheroe in Lancashire. 
In the var. flavescens and certain other of the paler varieties the epidermis 
or periostracum is often noticeably duplicated or doubled, resembling in 
this respect some of the tropical Bulimz. In the present species the outer 
film is usually darker in colour but very deciduous and frequently only 
perceptibly preserved on the body-whorl. 
In the thinner varieties the outer lip is not thickened and beautifully 
rounded as in typical shells, but is always thin and delicate with a white 
submarginal rib. 
The species is very closely simulated in its shell characters by several 
Euadeniate species occupying the Pacific coast of North America, but the 
internal organization is of quite a different type. 
