548 



THE AZOIC SYSTEM AND ITS SU13DJVISI0NS. 



Archaian is only theoretically fossiliferous. He admits that "no dis- 

 tinct remains of plants have been found in it." Yet, as his theoretical 

 views demand that plants should have existed before animals, he has 

 no hesitation in asserting that the presence of graphite is *' strong evi- 

 dence that plants of some kind were abundant." He even goes so far 

 as to state what these plants " must have been," namely, marine Algce^ 

 lichens, and fungi. At the same time, although admitting that the 

 Eozoon is a somewhat doubtful organism, he thinks that " animals of 

 the lowest division of animal life were prohahli/ abundant *' (in the 

 Archaean). 



If it be true, as Dana believes, that there existed, at a time previous 

 to the epoch of the Lower Silurian, an abundance of animal and vege- 

 table life, then the strata deposited at the time this life existed should 

 be enrolled among the fossiliferous groups, with a special name indicat- 

 ing the relations which this life held to that of succeeding groups. They 

 certainly should not be called Azoic, nor should they, on the other hand, 

 be designated as Archaean, that name being used at the same time to 

 include rocks necessarily destitute of traces of life and belonging to 



another epoch. 



The truth is, however, that — so far as the present state of our knowl- 

 edge goes — the ahimdance of life with which the Azoic is endowed is only 

 a theoretical abundance. One could not well make a new pala^ontological 

 subdivision based on graphite and calcite ; hence the theoretically zoic 

 rocks have had, of necessity, to remain with the practically azoic. 

 Whenever a new fauna shall have been clearly recognized as actually 

 existing below the Primordial, then the fact will no doubt receive wel- 

 come recognition, and the '* Age " or *' Epoch " be designated in accor- 

 dance with the nature of the fauna thus made known. 



Dana, however, not only includes in his Archxan the Azoic Series of 

 Foster and Whitney, by him considered, on theoretical grounds, as being 

 a fossiliferous formation ; but he embraces under that designation, not 

 only the granites and old volcanic rocks associated with the Azoic, and 

 which took their present position before the lowest Silurian strata were 

 deposited, but all eruptive, and indeed all crystalline rocks, with the 

 exception of such as are the result of the metamorphism of strata of 

 Silurian or post-Silurian age. 



This is not only the necessary and logical inference from Dana's defini- 

 tion of the term Archsean, but it results clearly from his special desig- 

 nation of the rocks which he embraces under that name. The crust of 

 the earth, according to his view, is Archaean; or, as he says, this is the 



