12 INTRODUCTION TO CONCHOLOGY. 



remind the traveller of Anchorites dwelling by the sea-side 

 in solitary tents. The Helices, or Snails^ slowly perambulate 

 the garden walks, with coverings that resemble the awnings 

 of broad- wheeled waggons. The Carclia, or Cockles, are 

 provided with thick coatings, which enable them to endure 

 the rough beating of a boisterous sea ; and the shells of 

 such species as are fragile and transparent, and scarcely able 

 to resist the slightest pressure, are found in still ponds and 

 muddy ditches. Some possess a solvent property, and are 

 thus enabled, by little or no expenditure of muscular power, 

 to effect important changes in their condition. 



Snails produce indentures in limestone walls even when 

 quietly at rest. Flwlades pierce the hardest limestone rocks, 

 and increase in size wliile remaining willing prisoners within 

 stone walls, without the slightest injury to their delicate 

 and highly finished shells. The Cowry, when arrived at 

 maturity, has even the power of partially dissolving a con- 

 siderable portion of his shell, and repairing or enlarging it, 

 according to his exigencies. Thus also has the Cone ; when 

 young, the inner spiral partitions of his shell are thick and 

 solid, but when adult they are absorbed to a degree of thin- 

 ness, which, at an earlier period, would not have been strong 

 enough to support the primitive structure. Some mollusks 



