26 FRIENDS WORTH KNOWING. 
nearer the north pole than any other known shell. Yet it 
is a remarkable fact, that, however erratic and extensive 
may be the range of the genera to which they belong, the 
majority of the species of pulmonates of all sorts have an 
extremely limited habitat, in some cases comprising only a 
few square rods. A second noteworthy fact, obtaining in 
no other extensive group of animals, is, that many more 
species of land shells exist in the islands than on the conti- 
nents of the world. Mr. A. R. Wallace accounts for this 
eurious fact by explaining how certain influences make isl- 
ands—particularly if long insulated 
HELIGES IN HUMBLE CIRCUMSTANCES. 
