THEIR DISTRIBUTION. 
83 
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 living 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 belong to animals which 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 construc- 
tion of the creature, and the uses for which it was created. 
From examinations conducted on this principle, it is inferred that 
the secondary strata contain remains of marine, lacustrine, and terrestrial 
M 2 
