AGES OF NATURE. 



401 



the sturgeon, arrested, as it were, in their development ; since 

 we have shown that the 



Bturgeon, in its organiza- 

 tion, agrees, in many re- 

 spects, with the cod or 

 salmon in their early age. 

 669. Finally, there 

 was, during the palaeozoic 

 age, less variety among 

 the animals of the differ- 

 ent regions of the globe ; 

 and this may be readily 

 explained by the peculiar 

 configuration of the earth 

 at that epoch. Great 

 mountains did not then 

 exist ; there were neither 

 lofty elevations nor deep 

 depressions. The sea co- 

 vered the greater part, if 

 not the whole, of the sur- 

 face of the globe ; and the 

 animals which then exist- 

 ed, and whose remains 

 have been preserved, were 

 all, with the exception or 

 the reptiles which have 

 left their foot-marks on 

 the Potsdam sandstone, 

 aquatic animals, breathing 

 by gills. This wide dis- 

 tribution of the waters im- 

 pressed a very uniform 

 character upon the whole 

 animal kingdom. Between 

 different zones and conti- 

 nents, no such strange T 



c \ i-ir L Yis.SSO.Coccosteuscuspidatus. A^ass. 

 contrasts of the different 



types existed as at the present epoch. The same gener;., and 

 often the same species, were found in the seas of America, 

 Europe, Asia, Africa, and New Holland ; from which we must 



D D 



