SILURIAN SYSTEM: AGE OF INVERTEBRATES. 



301 



Fig. 289.— Paradoxides Bohemi- 

 cu8, Foreign. 



character of all fossil faunas, it seems certain that great abundance and 

 variety of. life existed already in these early seas. Of this life the tri- 

 lobites, by their size, their abundance, their variety, and their high 

 organization, must be regarded as the dominant type. Among the 

 largest trilobites known at all are some from this period. The Para- 

 doxides, represented in Figs. 289 and 290, attained a length of twenty 

 inches. English beds of 

 the same age furnish 

 specimens of the same 

 genus two feet long. 



We give in the above 

 figures a few of the more 

 remarkable primordial 

 forms taken from the 

 rocks of this country, 

 and of foreign countries. 

 They are intended only 

 to give a general idea of 

 the fullness and variety 

 of the primordial life ; 

 the affinities of these fos- 

 sils will be discussed 

 hereafter. 



General Remarks on First Distinct Fauna. — There are several 

 points of great philosophic interest suggested by the nature of these 

 first organisms : 



1. Plants in this, and in all other geological periods, are far less 

 numerously represented in a fossil state than animals. This can not be 

 because animals were more abundant than plants, for since the animal 

 kingdom subsists on the vegetable kingdom, and since every animal 

 consumes many times its own weight of food, plants must have been 

 always more abundant than animals. The true reason of the greater 

 abundance of animal remains is to be found in the fact that the hard 

 parts of animals are far more indestructible than any portion of vege- 

 table tissue. 



2. At the end of the Archaean times — when the Archsean volume 

 closed — we find, if any, only the lowest Protozoan life. But with the 

 opening of the next era, apparently with the first pages of the next 

 volume, we find already all the great types of structure except the 

 vertebrata. And these are not the lowest of each type, as might have 

 been expected, but already trilobites among Articulata, and Cephalo- 

 pods among Mollusca — animals which can hardly be regarded as lower 

 than the middle of the animal scale. 



We must not hastily conclude, however, that these widely-divergent 



Fig. 290.— Paradoxides 

 Harlan i, x £ (after 

 Rogers), American. 



