50 THE MEDALS OF CREATION. Cuap. III. 
The scales of fishes, and the integuments of marine rep- 
tiles, are not the only vestiges of the dermal coverings of 
vertebrated animals that are preserved by mineralization. 
Traces of the wing-integument of flying reptiles, and of the 
feathers of birds, are sometimes manifest: and even when 
every atom of the original structure has perished, the im- 
pression may remain, and afford satisfactory results. The 
footmarks of unknown animals are often preserved in the 
rocks, and the imprints of the feet of several species of 
bipeds, presumed to be birds of colossal size, in tracks as 
distinct as if but recently made, have been discovered in 
the New Red sandstone of North America; in the section 
on fossil birds, this highly interesting subject will be fully 
explained. 
The student, even from this brief review, will perceive 
how many valuable facts may be unnoticed, and irretriey- 
ably lost, unless attention be paid to the various circum- 
stances under which fossil remains are presented to his 
notice. 
Of the invertebrated orders, the most durable, and conse- 
quently the most numerous relics, are shells and corals. 
The integuments of the eyes, antennz, and wings of Insects 
occur ; and the shelly coverings of Crustaceans are not 
uncommon; those of the Echinoderms, the Star-fishes, and 
of the Crinoidea or Lily-animals, are very abundant in cer- 
tain deposits. Instructions for the collection and arrange- 
ment of these fossils will be given in the chapters in which 
they are severally described. 
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