280 FORMS OF LIFE CHANGING [CHAP. XL 



information 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 Mas- 

 todon 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 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 some degree allied, and from not in- 

 cluding 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 world, has greatly struck 

 those admirable observers, MM. de Verneuil and d'Archiac. After- 

 referring to the parallelism of the palaeozoic forms of life in various 

 parts of Europe, they add, " If, struck by this strange sequence, 

 we turn our attention to North America, and there discover a 

 series of analogous phenomena, it will appear certain that all these 

 modifications of species, their extinction, and the introduction of 

 new ones, cannot be owing to mere changes in marine currents or 

 other causes more or less local and temporary, but depend on 

 general laws which govern the whole animal kingdom." M. Bar- 

 rande has made forcible remarks to precisely the same effect. It 

 is, indeed, quite futile to look to changes of currents, climate, or 

 other physical conditions, as the cause of these great mutations in 

 the forms of life throughout the world, under the most different 

 climates. We must, as Barrande has remarked, look to some 



