METAMORPHOSES OF ANIMALS. 185 



those of the most ancient deposits have, in general, preserved 

 only the apophyses of their vertebra, whilst the vertebrae 

 themselves are wanting. Were the Sturgeons of the Amer- 

 ican rivers to become petrified, they would be found in a 

 similar state of preservation. As the apophyses are the 

 only bony portions of the vertebral column, they alone 

 would be preserved. Indeed, fossil Sturgeons are known, 

 which are in precisely this condition. 



395. From the fact above stated, we may conclude that 

 the oldest fossil fishes did not pass through all the metamor- 

 phoses which our osseous fishes undergo ; and, consequently, 

 that they were inferior to analogous species of the present 

 epoch which have bony vertebrae. Similar considerations 

 apply to the fossil Crustacea and to the fossil Echinoderms, 

 when compared with living ones, and will, probably, be 

 true of all classes of the Animal Kingdom, when fully studied 

 as to their geological succession. 



16* 



