THEIR DISTRIBUTION. Ill 



lime, which accounts for their high specific gravity. Bones of fishes and 

 aquatic reptiles retain their cariose texture, and frequently their original 

 composition. 



DISTRIBUTION OF FOSSILS. 



MODERN naturalists have discovered in the earth the remains of 

 several hundred different plants, and several thousand kinds of animals. 

 The peculiarities of form and structure among fossils are as constant and 

 defined as among the li ving productions of nature, and the species are 

 often as well distinguished. Upon comparing them with existing races, 

 it is discovered that they are generally quite distinct ; so that the fossil 

 tribes, in some degree, appear like a separate creation, and have been 

 elegantly termed " organic remains of a former world." But though 

 different in detail, the ancient and existing races of organic nature are 

 alike in generalities, and analogous in essential points of structure ; 

 and forcibly urge us to conclude that they were destined for similar 

 modes of life. In the present economy of nature, plants of particular 

 structure are appointed to exist under particular circumstances ; shells of 

 certain forms are peculiar to water, and others live habitually on land ; 

 and, generally, so constant is the agreement in the structure and functions 

 of organic beings, that from the one we may infer the other. Who, that 

 views the striking general resemblance of fossil and recent bodies, and 

 considers the similar accidents to which both have been exposed, can 

 hesitate for a moment to admit that conclusions drawn from examination 

 of the structure of fossils, are as valid as those which are inferred from 

 recent examples. The principle of investigation is in both cases the same, 

 viz. the inevitable accordance between the construction of the creature, 

 and the uses for which it was created. 



From examinations conducted on this principle, it is inferred that 

 the secondary strata contains remains of marine, lacustrine, and terrestrial 



