304 FORMS OF LIFE CHANGING Ciiai-. X. 



the productions of llie land and of fresh water at distant points 

 clianfj^e in the same jiarallcl manner. We may doubt wliethcr 

 thoy have tluis changed: if the Meg-atherium, Milodon, Macra- 

 iiclicnia, and Toxodon had been brought to Europe from La 

 Plata, without any information in regard to their geological 

 position, no one would have suspected that they had coexisted 

 with sea-shells all still living; but as these anomalous monsters 

 coexisted with the Mastodon and Horse, it might at least have 

 been inferred that they had lived during one of the later ter- 

 tiary stages. 



When the marine forms of life are spoken of as haWng 

 changed simultaneously throughout the world, it must not be 

 supposed that tliis expression relates to the same thousandth 

 or ten-thousandth year, or even that it has a very strict geologi- 

 cal 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 

 Avhole glacial epoch) Avcre compared Avith those now existing 

 in South America or in Australia, the most skilful naturalist 

 would hardly be able to say whetlicr the present or the pleis- 

 tocene inhabitants of Europe resembled most closely those of 

 the southern hemisphere. So, again, several highly-competent 

 obs(>rvers 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 inhabit- 

 ants of Europe ; and if this be so, it is e\ddent that fossilifer- 

 ous beds now being 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 ma- 

 rine formations, namely, the upper pliocene, the pleistocene 

 and strictly modern beds, of Europe, North and South Amer- 

 ica, and Australia, from containing fossil remains in some de- 

 gree 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, in the 

 above large sense, at distant parts of the Avorld, has greatly 

 struck those admirable observers, MM. do Verneuil and d'Arcli- 

 iac. After referring to the parallelism of the paleozoic forms 

 of life in various pails of Europe, they 'add : " If. struck by tliis 

 strange sequence, Ave turn our attention to North AmcricM, 

 and there discover a series of analogous iihenomena, it wi!.' 



