30 EXTINGY MONSTERS 
some of the most ancient of rocks, such as those of the Cambrian 
system, jelly-fish have left indelible impressions of their soft 
round bodies! 
Speaking of the wonderfully enduring nature of certain im- 
pressions known to geologists, the sagacious Dean Buckland said, 
in an address to the Geological Society: “The historian or the 
antiquary may have traversed the fields of ancient or of modern 
battles, and may have pursued the line of march of triumphant 
conquerors, whose armies trampled down the most mighty 
kingdoms of the world. The winds and storms have utterly 
obliterated the ephemeral impressions in their course. Not a 
track remains of a single foot or a single hoof of all the countless 
millions of men and beasts whose progress spread desolation over 
the earth. But the reptiles that crawled upon the half-finished? 
surface of our infant planet have left memorials of their passage, 
enduring and indelible. Centuries and thousands of years have 
rolled away, between the time in which these footsteps were 
impressed by tortoises upon the sands of their native Scotland 
and the hour when they were again laid bare and exposed to our 
curious and admiring eyes. Yet we behold them stamped upon 
the rock, distinct as the track of the passing animal upon the 
recent snow; as if to show that thousands of years are but as 
nothing amidst eternity, and, as it were, in mockery of the fleeting 
perishable course of the mightiest potentates among mankind.” ? 
Every form of animal life that, writhing, crawling, walking, 
running, hopping, or leaping, could leave a track, depression, or 
footprint behind it, might thereby leave similar lasting evidence 
of its existence and also, to some extent, of its nature. The 
1 This expression is a survival from the teaching in vogue fifty years ago. 
The world was not in an unfinished state during the period of the New Red 
Sandstone, 
* Bridgewater Treatise, vol. i. p. 251. 
