290 ON THE ORIGIN OF SPECIES 



sometimes are similarly characterised in such trifling 

 points as mere superficial sculpture. Moreover other 

 forms, which are not found in the Chalk of Europe, but 

 which occur in the formations either above or below, are 

 similarly absent at these distant points of the world. In 

 the several successive palaeozoic formations of Russia, 

 Western Europe and North America, a similar parallel- 

 ism in the forms of life has been observed by several 

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

 European and North American tertiary deposits. Even 

 if the few fossil species which are common to the Old 

 and New Worlds be kept wholly out of view, the general 

 parallelism in the successive forms of life, in the stages 

 of the widely separated palaeozoic and tertiary periods, 

 would still be manifest, and the several formations 

 could be easily correlated. 



These observations, however, relate to the marine 

 inhabitants of distant parts of the world : we have not 

 sufficient data to judge whether the productions of the 

 land and of fresh water change at distant points in the 

 same parallel manner. We may doubt whether they 

 have thus changed : if the Megatherium, Mylodon, 

 Macrauchenia, 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 co-existed with still living sea- shells ; 

 but as these anomalous monsters co-existed with the 

 Mastodon and Horse, it might at least have been in- 

 ferred 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 day 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 



