THE REIGN OF REPTILES. 175 



their habits, having feet for walking instead of flat, oar- 

 like extremities for swimming. 



These forms all disappeared with the dawn of a new era. 

 Their bones lie buried in the geological cemeteries of Eu- 

 rope. It is almost incredible that information so exact can 

 be drawn from the few scattered fragments which have 

 been brought to light ; but such is the unity and persist- 

 ence of plan which runs through the different classes of the 

 animal kingdom, that a single tooth, whether of a living or 

 extinct species, will often suffice to enable the expert to 

 disclose all the zoological relationships of the animal to 

 which it belonged, to delineate its form, and size, and hab- 

 its of life ; as the architect from a single capital rescued 

 from a ruined edifice can declare not only the general 

 style of the entire architecture, but can reproduce the size 

 and proportions of the temple whose spirit and method it 

 embodies. Not less sublime than the work of the astron- 

 omer, who sits in his observatory, and, by the use of a few 

 figures, determines the existence and position in sjDace of 

 some far-off, unknown orb, is that of the paleontologist — 

 the astronomer of time-worlds — who, from the tooth of a 

 reptile, or the bony scale of a fish found thirty feet deep in 

 the solid rock, declares the existence, ages ago, of an ani- 

 mal form which human eyes never beheld — a form that 

 passed totally out of being uncounted centuries before the 

 first intelligent creature was placed upon our planet — and 

 by laws as unerring and uniform as those of the mathe- 

 matics, proceeds to give us the length and breadth of the 

 extinct form; to tell us whether it lived upon dry land, in 

 marshes, or in the sea; whether a breather of air or water, 

 and whether subsisting upon vegetable or animal food. It 

 is this unity of the laws of animal life and organization 

 running through the whole chain of existence, whether past 

 or present, whether extinct or recent, that constitutes the 



