102 FOEMS OF LIFE CHANGING [Chap. XL 



these 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 

 glacial epoch) were compared with those now existing 

 in South America or in Australia, the most skilful 

 naturalist would hardly be able to say whether the 

 present or the pleistocene inhabitants of Europe re- 

 sembled 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 

 inhabitants of Europe ; and if this be so, it is evident 

 that fossiliferous 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 

 Australia, 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 simultaneously, 



