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8 SUPPLEMENTARY SECTION. 



TABLE OF BRIAN AND CARBONIFEROUS SPECIFIC TYPES. 



Erian Types. Koprpscnted in Carbonlferoiw— Erlan Typon. Ueproaentod In Carboniferoiia— 



Of the above forms, fifty-one in all, found in the Erian of Eastern 

 America, all, except the four last, are certainly distinct specific types. Of 

 these only four reappear in the Carboniferous under identical species, but 

 no less than twenty-six reappear under representative or allied forms, 

 somo at least of which a derivationist might claim as modified descendants. 

 On the other hand nearly one half of the Devonian types are unknown 

 in the Carboniferous, while there remain a very large number of Car- 

 boniferous types not accounted for by anything known in the Devonian. 

 Farther, a very poor flora, including only two or three types, is the prede- 

 cessor of the Erian flora in the Upper Silurian, and the flora again becomes 

 poor in the Upper Devonian and Lower Carboniferous. Every new species 

 discovered must more or less modify the above statements, and the whole 

 Erian flora of America, as well as the Carboniferous, requires a thorough 

 comparison with that of Europe before general conclusions can be safely 

 drawn. In the meantime I may indicate the direction in which the facts 

 seem to point, by the following general statements : — 



1. Some of the forms reckoned as specific in the Devonian and Car- 

 boniferous r.^ay be really derivative races. There are indications that such 

 races may have originated in one or more of the following ways : — (1) By 

 a natural tendency in synthetic types to become specialized in the direction 



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