) INTRODUCTION. 
we observe that a smaller number of species are to be met 
with in the older, than in the newer rocks, we may assume, 
that new forms were less frequently called into existence 
during the earlier geological epochs. It is evident, there- 
fore, that each great change to which our globe was sub- 
jected, was also marked by the successive production and 
obliteration of certain races of Mollusks. 
On a rigid examination of strata, we have incontestible 
proofs of the progressive development of their animal con- 
tents. We find that certain species have been endowed 
with powers to resist the changes which took place, or 
must have lived in situations remote from the active agents 
of destruction ; while others, of a high structure, have been 
swept away in comparatively short periods. 
It is a remarkable fact, regarding the distribution of 
organic remains in the older deposits, that the same forms 
are found in rocks of the same age in all parts of the globe. 
In these strata, equivalent to our Lias and Qolite, the 
same forms have been found in England, Russia, Norway, 
Southern Africa, the Falkland Islands, (our antipodes,) and 
even in the Himalaya Mountains, and at Fernando Po. 
Although the older strata contain vast masses of fossil 
remains, yet, as we have above observed, the number of 
species is exceedingly limited, as compared with those of 
the newer deposits. 
Conchology was long considered as a trifling pursuit, and 
tending to no useful purpose; but we have found, that 
through an intimate acquaintance with it, we are indebted 
fora more thorough knowledge of the strata which com- 
pose the different formations. The highest authorities of 
the present day all concur in this opinion. Professor 
Buchland says, “ Concurrent with the rapid extension of 
our knowledge of the comparative anatomy of extinct 
families of the ancient inhabitants of the earth, has been 
the attention paid to Fossiz Concnotoey, a subject of 
vast importance in investigating the records of the changes 
that have occurred upon the surface of the globe.” And 
Mr Lyell, in descanting upon fossil remains, says, “ The 
Testacea (shells) are by far the most important class of 
organic beings w hich have left their spoils in the subaqueous 
deposits ; and they have been truly said to be the medals 
which Nature has chiefly selected to record the history of 
the former changes of the globe. There is scarcely any 
great series of strata that does not contain some marine or 
