324 GEOLOGICAL SUCCESSION, Chap. X. 



don and Horse,' it might at least have been inferred that 

 they had lived during one of the later tertiary stages. 



When the marine forms of life are spoken of as 

 having changed simultaneously throughout the world, 

 it must not be supposed that this expression relates to 

 the same thousandth or hundred-thousandth year, or 

 even that it has a very strict geological sense ; for if 

 all the marine animals which live at the present clay in 

 . Europe, and all those that lived in Europe during the 

 pleistocene period (an enormously remote period as 

 measured by years, including the whole glacial epoch), 

 were to be compared with those now living in South 

 America or in Australia, the most skilful naturalist 

 would hardly be able to say whether the existing or the 

 pleistocene inhabitants of Europe resembled most closely 

 those of the southern hemisphere. So, again, several 

 highly competent observers believe that the existing 

 productions of the United States are more closely related 

 to those which lived in Europe during certain later ter- 

 tiary stages, than to those which now live here: and 

 if this be so, it is evident that fossiliferous beds de- 

 posited at the present day on the shores of North 

 America would hereafter be liable to be classed with 

 somewhat older European beds. Nevertheless, looking 

 to a remotely future epoch, there can, I think, be little 

 doubt that all the more modern marine format ions, 

 namely, the upper pliocene, the pleistocene and strictly 

 modern beds, of Europe, North and South America, and 

 Australia, from containing fossil remains in some degree 

 allied, and from not including those forms which are 

 only found in the older underlying deposits, would be 

 correctly ranked as simultaneous in a geological sense. 



The fact of the forms of life changing simultaneously, 

 in the above large sense, at distant parts el' the world, 

 lias greatly struck those admirable observers, Mil, 



