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tracing the affinity of extinct to existing species ; lie will thus note 

 their differences, learn their habits, and form a notion of the con- 

 ditions under which these animals of the past existed — he will 

 marvel that the worm should have left its track and burrows, the 

 ebbing tide its ripple, and the raindrop its record on the surface of 

 the rocks ; he will observe the trilobite, one of the earliest crus- 

 taceans, attain its greatest developement in the Silurian period, and 

 gradually become extinct in the carboniferous rocks — he will be 

 struck with its varied form, elaborate structure, and the countless 

 facets of its eye — he will compare the Orthoceratites and the 

 numerous Cephalopods with their allies, the extinct Ammonites, 

 and the Nautilus of the present seas ; and will see in each species 

 the same chambered structure and the same provision for floating 

 on the surface of the water, although the forms are so various and 

 unlike ; he Avill admire the numerous and varied series of corals 

 and Crinoids in the limestones, the elegant Star-fishes and number- 

 less Mollusca of the Silurian seas, and when the these last are 

 gradually dying away, he will see the Pterygoti and Euryptendse, 

 the largest of Crustaceans, for a brief time the principal occupants 

 of the deep, in their turn succeeded by the Fishes, and at last a 

 Flora, of which faint traces before appeared, of gigantic Ferns, 

 Palms, and Conifers, covering the service of the earth with a 

 luxuriant tropical vegetation, and he will rise from the contempla- 

 tion of the subject more and more impressed with the infinite 

 wisdom, power, and goodness of God in the works of creation. 



"When we consider in how few places the crust of the earth is 

 broken, and how seldom, when the rocks are exposed to our view, 

 we have an opportunity of arriving at their contents, we may rea- 

 sonably expect that fresh discoveries will from time to time reward 

 the persevering searcher of the Paleozoic rocks. We know how 

 the accidental discovery of a Star-fish at Church-hill, led to a 

 further search, and an addition of thirteen or fourteen new species 

 of Star-fishes to the three or four species jireviously known in the 

 Silurian rocks, and to the discovery of several new species of 



