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SUFPLEMENTART SECTION. 5 



floras of North America, we obtain some data which may guide us in 

 arriving at general conclusions. The Erian flora is comparatively poor, and 

 its types are in the main similar to those of the Carboniferous. Of those 

 types a few only re-appear in the Middle Coal formation under identical 

 forms ; a great number appear under allied forms ; some altogether disap- 

 pear. The Erian flora of New Brunswick and Maine occurs side by side 

 with the Carboniferous of the same region ; so does the Erian of New 

 York and Pennsylvania with the Carboniferous of those states. Thus we 

 have data for the comparison of successive floras in the same region. In 

 the Canadian region wo have, indeed, in direct sequence, the floras of the 

 Upper Silurian, the Lower, Middle, and Upper Erian, and the Lower, 

 Middle," and Upper Carboniferous, all more or less distinct from each other, 

 and affording an admirable series for comparison in a region whose geo- 

 graphical features are very broadly marked. All these floras are composed 

 in great part of similar types, and probably do not indicate very dissimilar 

 general physical conditions, but they are separated from each other by the 

 great subsidences of the Corniferous limestone and the Lower Carbon- 

 iferous limestone, and by the local but intense subterranean action which 

 has altered and disturbed the Erian beds towards the close of that period. 

 Still, none of these changes was universal. The Corniferous limestone 

 is absent in Gasp^, and probably in New Brunswick, where, consequently, 

 the Elian flora could continue undisturbed during that long period. The 

 Carboniferous limestone is absent from the slopes of the Appalachians in 

 Pennsylvania, Tvhere a retreat may have been afforded to the Upper Erian 

 and Lower Carboniferous floras. The disturbances pt the close of the 

 Erian were limited to those eastern regions where the great limestone- 

 producing subsidences were unfelt, and, on the other hand, are absent in 

 Ohio, where the subsidences and raarine conditions were almost at a maxi- 

 mum. 



Bearing in mind these peculiarities of the area in question, we may now 

 group in a tabular form the distinct specific types recognized in the Erian 

 system, indicating, at the same time, those which are represented by 

 identical species in the Carboniferous, those represented by similar species 

 of the same general type, and those not represented at all. For example, 

 Calamites canncefurmis extends as a species into the Carboniferous ; 

 Aster ophyllites latifolia does not so extend, but is represented by closely 

 allied species of the same type ; Prototaxites disappears altogether before 

 we reach the- Carboniferous, 



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