298 FORMS OF LIFE CHANGING [Chap. XI. 



but which occur in the formations either above or below, occur in 

 the same order at these distant points of the world. In the several 

 successive palaeozoic formations of Russia, Western Europe, and 

 North America, a similar parallelism in the forms of life has been 

 observed by several authors : so it is, according to Lyell, with the 

 European and North American tertiary deposits. Even if the few 

 iossil species which are common to the Old and New Worlds were 

 kept wholly out of view, the general parallelism in the successive 

 forms of life, in the palaeozoic and tertiary stages, would still be 

 manifest, and the several formations could be easily correlated. 



These observations, however, relate to the marine inhabitants of 

 the world : we have not sufficient data to judge whether the pro- 

 ductions of the land and of fresh water at distant points change in 

 the same parallel manner. We may doubt whether they have thus 

 changed : if the Megatherium, Mylodon, Macrauchenia, and Toxo- 

 don had been brought to Europe from La Plata, without any in- 

 formation in regard to their geological position, no one would have 

 suspected that they had co-existed with sea-shells all still living ; 

 but as 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 jxleistocene period (a very remote period as 

 measured by years, including the whole glacial epoch) were com- 

 pared 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 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 

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

 ferous 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 sorce degree allied, and from not including those 



