compared with that of Europe. 121 



These mineralogical transitions, which one would expect in 

 a country free fi'om disturbances, would not, however, obscure 

 the proofs of a pai'allel development of the animal kingdom 

 in the two continents : for if, leaving aside the difficulties of 

 fixing the limits between the systems, we compare the sys- 

 tems together, or, still better, one by one the groups of which 

 they are composed, we acquire the conviction that identical 

 species have lived at the same epoch in America and in 

 Europe, that they have had nearly the same duration, and 

 that they succeeded each other in the same order. We have 

 endeavoured to prove that the first traces of organic life in 

 countries the most remote, appear under forms nearly alike, 

 at the base of the Silurian system, and that the same types, 

 often the same species, are successively, and in parallel 

 order, developed through the entire series of the palaeozoic 

 beds. If we have not succeeded in lifting the veil which still 

 hides from us the cause of this grand phenomenon, perhaps at 

 least our observations demonstrate the insufficiency of those 

 causes by which certain authors seek to explain it. They 

 prove, in eff"ect, that the phenomenon itself is independent of 

 the influences which the depth of seas* exercise upon the dis- 

 tribution of animals ; for if, in certain countries, the Silurian 

 deposits prove a deep sea, they have, on the contrary, in the 

 state of New York, a littoral character. They prove, in 

 fine, that in its general chai'acter it is equally independent of 

 the upheavings which have affected the surface of the globe ; 

 for, from the eastern frontier of Russia even to Missouri, dis- 

 tant from or near the lines of dislocation, in the horizontal 

 beds, as well as in those which are disturbed, the law accord- 

 ing to which it is accomplished appears to be uniform. — {^The 

 American Journal of Science and Arts, vol. vii., p. 48.) 



* We do not pretend to say that the differences of depth in the seas had not 

 already an influence upon the distribution of animals ; it is to this circumstance, 

 on the contrary, that we attribute the more or less local fauna which we often 

 discover in the puljeozoic class. But these local faunie always afford some 

 species which connect them with the epoch to which they belong. They are 

 the exceptions {hors d^ceuvre), which do not derange the gejieral symmetry. 



