102 FORMS OF LIFE CHANGING [Chap. XL 



anomalous monsters co-existed with the Mastodon 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 year, or to the same century, or even that it 

 has a very strict geological sense; for if all the marine 

 animals now living in Europe, and all those that lived 

 in Europe during the pleistocene period (a very remote 

 period as measured by years, including the whole gla- 

 cial epoch) were compared with those now existing in 

 South America or in Australia, the most skilful natu- 

 ralist would hardly be able to say whether the present 

 or the pleistocene inhabitants of Europe resembled most 

 closely those of the southern hemisphere. So, again, 

 several highly competent observers maintain that the 

 existing productions of the United States are more 

 closely related to those which lived in Europe during 

 certain late tertiary stages, than to the present inhabi- 

 tants of Europe;' and if this be so, it is evident that fos- 

 siliferous beds now deposited 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 be little doubt 

 that all the more modern marine formations, namely, 

 the upper pliocene, the pleistocene and strictly modern 

 beds of Europe, North and South America, and Aus- 

 tralia, from containing fossil remains in some degree 

 allied, and from not including those forms which are 

 found only in the older underlying deposits, would be 

 correctly ranked as simultaneous in a geological sense. 



The fact of the forms of life changing simultaneous- 



