1S6 INTKODUCTIOX TO CONCHOLOGY. 



also the tints of terrestrial molliisks ; hence coucliologists 

 easily distinguish such as dwell on the ground from those 

 wliich climb the trunks of trees and feed among the 

 branches,, also such as inhabit regions of drought or ex- 

 cessive dew^ from those which are assigned to rainy and 

 woody districts. Bulimi present, in this respect, examples 

 of the deepest interest : they are distributed over the equa- 

 torial, the tropical, and warm temperate regions of the 

 earth, in specific assemblages, circumscribed as regards 

 their range, and exhibiting in their shells a very distinct 

 typical character. 



The molluscous inhabitants of the shells are much less 

 variable, and, being naturally sluggish, with limited powers 

 of locomotion, rarely migrate to any considerable distance, 

 even when not prevented by the natural barriers of seas, 

 or deserts, or mountain ranges. Owing to their frequently 

 dwelling in the branches of trees, Mr. Lovell Eeeve considers 

 them to be fitter subjects of investigation, with reference 

 to the laws of geographical distribution, than their relatives 

 the Helices, which are more habituated to dwell on the 

 ground, and are less influenced by local circumstances. 

 Some few Bulimi are, however, prone to remain on earth. 



