IN A SNAILERY. 27 



more productive than continents, and at the same time 

 liable to be deficient in enemies to snails. 



How has this curious distribution* come to pass? How 

 have seemingly impassable barriers been overcome, so that 

 closely related forms are now found at the antipodes ? 



Snails are of domestic tastes. " The Heathen painted be- 

 fore the modest women's doors Venus sitting upon a snail, 

 quce domi forta vocatur, called a House bearer, to teach 

 them to stay at home, and to carry their houses about with 

 them." They are also slow of pace, as a list of poets are 

 ready to stand up and testify ; but they have had a long 

 time in which to u get a good ready," first to start, and af- 

 terward to accomplish their travels, since their existence as 

 a race goes back to when dark forests of ferns waved their 

 heavy fronds over the inky palaeozoic bogs. Distance dis- 

 appears in the presence of such prodigious time. Lands 

 like our western plains, now an arid waste impassable to 

 rnollusks, in by - gone ages were clothed with dense and 

 limitless verdure, where every form of terrestrial life 

 abounded. Between the present and even the laying down 

 of those cretaceous sandstones that make the soil of our 

 level plains, the Rocky Mountains have been elevated from 

 an altitude at which any mollusk could probably have lived 

 upon their summits, until now they may be a barrier to 



