190 CONCHOLOGIST’S COMPANION. 
LETTER XI. 
FOSSIL SHELLS. 
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From the natural history of testaceous animals, the 
transition is easy to those Fossil Shells, which di- 
versify the strata of the earth. 
The lowest, and most level parts, of the great 
globe which we inhabit, exhibit, when penetrated to 
a considerable depth, horizontal strata, composed of 
various substances, and, generally, containing innu- 
merable marine productions. Such is also the case 
in more elevated regions, where, occasionally, fossil 
shells so far preponderate, as to constitute the entire 
body of the stratum. These are generally in such a 
perfect state of preservation, that even the smallest 
retain their most delicate parts, and their sharpest 
ridges. They are found in situations far above the 
