THE ERIAN OR DEVONIAN FORESTS. 



109 



either the plants of two distinct beds, one Lower Carboniferous and 

 the other Upper Devonian, have been near to or in contact with each 

 other and have been intermixed, or else that in this high northern 

 latitude, in which (for reasons stated in my " Report on the Devo- 

 nian Flora " *) I believe the Devonian plants to have originated, there 

 was an actual intermixture of the two floras. In America, at the 

 base of the Carboniferous of Ohio, a transition of this kind seems 

 to occur; but elsewhere in northeastern America the Lower Car- 

 boniferous plants are usually unmixed with the Devonian. 



Dr. Heer, however, proceeds to identify these plants with those 

 of the American Chemung, and even with those of the Middle De- 

 vonian of New Brunswick, as described by me — a conclusion from 

 which I must altogether dissent, inasmuch as the latter belong to 

 beds which were disturbed and partially metamorphosed before the 

 deposition of the lowest Carboniferous or " Subcarboniferous " beds. 



Dr. Heer's error seems to have arisen from want of acquaintance 

 with the rich flora of the Middle Devonian, which, while differing in 

 species, has much resemblance in its general facies, and especially in 

 its richness in ferns, to that of the coal-formation. 



To geologists acquainted with the stratigraphy and the accom- 

 panying animal fossils, Dr. Heer's conclusions will of course appear 

 untenable ; but they may regard them as invalidating the evidence 

 of fossil plants ; and for this reason it is, I think, desirable to give 

 publicity to the above statements. 



I consider the British equivalent of the lower coal-measures of 

 eastern America to be the lower limestone shales, the Tweedian 

 group of Mr. Tate (1858), but which have sometimes been called the 

 " Calciferous Sandstone " (a name preoccupied for a Cambrian group 

 in America). This group does not constitute " beds of passage " to 

 the Devonian, more especially in eastern America, where the lower 

 coal-formation rests unconformably on the Devonian, and is broadly 

 distinguished by its fossils. 



The above notes would not have been extended to so great 

 length, but for the importance of the Erian flora as the precursor 

 of that of the Carboniferous, and the small amount of attention 

 hitherto given to it by geologists and botanists. 



* " Geological Survey of Canada," 1871. 



