THE CLIMATE OF ACADIA IN THE EARLIEST TIMES. 5 



Then in regard to the shell-fish (molluscs), those which 

 exist in the ocean at the present day, are governed by certain 

 laws of distribution, which confine some kinds to warm seas 

 and others to cold. And farther, we may note that the 

 majority of shell-fish (molluscs) of the ocean are shore 

 dwellers. An exception to this rule in the shell-fish is the 

 ancient class of Lampshells, now reduced to a small number 

 of species, but once universally prevalent, exceedingly numer- 

 ous, and of great variety. This class of the Lampshells, or 

 Brachiopods, was spread in the earliest ages both in shallow 

 and deep waters, as they are at the present day. 



The richest collecting grounds for the common molluscs 

 are at this day found on the hot, tropical shores of the East 

 and West Indies, and among the coral islands of the Pacific. 

 Here the great marine snails and bivalves are to be found in 

 immense numbers, and are of great variety and beauty. 



Coming north a marked change in the appearance of these 

 animals may be observed ; the highly burnished shells of the 

 tropics disappear, the shell itself, as a rule, is thinner and is 

 covered by a dull colored skin, and the great variety of species 

 of the south is replaced by a monotonous assemblage in which, 

 while the individuals are numerous, the species are fewer 

 than in tropical seas, and many are small. We may there- 

 fore conclude that warm, clear seas have always been the 

 favorite homes of reef-building corals and the marine snails 

 and bivalve shell-fish, as we know them to be at the present 

 day. 



But while there are thus certain forms of life which 

 flourish along shores and in warm shallow seas, the open 

 ocean is not without inhabitants, though these in their more 

 lowly forms are not of a kind to attract attention ; yet owing 

 to their immense numbers their skeletons have been of great 

 importance in building up the layers of the earth's crust. 



