134 INTRODUCTION. 



upon them. We have frequently noticed that "when 

 in a state of confinement, Helix concava, itself not an 

 abundant species, will generally destroy other species 

 which are kept with it ; and the animal of Cfla7idina 

 truncata, which we have occasionally had in captivity, 

 has uniformly destroyed those of the other genera and 

 species placed within its reach. In the same manner 

 Limax variegatus, when kept a few days without food, 

 has devoured the weaker Limax agrestis, leaving no 

 vestige of them except the rudimentary shell. We have 

 also been informed, on what we consider to be good au- 

 thority, that a foreign species, believed to be Jlelix 

 nemoralis, which existed formerly in great numbers in 

 Charleston, S. C, was completely exterminated by Buli- 

 mus decoUatus, a foreign species also, which now flour- 

 ishes there in abmidance. In this case, however, the 

 destruction of the one species, though subsequent to the 

 introduction of the other, might not have had any con- 

 nection with it. Birds also make great havoc among 

 them, where the woods are so far opened as to permit 

 the entrance of such of them as do not usually fre- 

 quent the forest. They seize the shell with their beaks, 

 and bearing it to a prostrate tree or log, break it with 

 repeated blows of the point of the bill, and extract the 

 soft animal. It is not uncommon to find numerous 

 broken shells about a spot in the woods which has been 

 selected by the bird as the seat of its operations. The 

 little heaps of shells in the woods are by some supposed 

 to be due to the agency of squirrels, and not of birds, 



