FOSSIL PLANTS. 501 



ject have been published at different times, with the modifications induced by 

 the progress of the researches, a summary of what is positively ascertained as 

 yet on the stratigraphical distribution of the vegetation of the Coal Measures 

 is not out of place in this Report. (1) 



When researches are restricted to a limited area, or to basins of small extent, 

 marked differences are recognizable in the species of vegetable remains in the 

 shales, as well as in the essential vegetable components of each bed of coal. It 

 is, then, an easy task to ascertain the relative position of the coal strata from 

 the comparison of these remains. But when researches are extended over a 

 wider area, changes of vegetation, evidently caused by geographical distribu- 

 tion, become more and more appreciable, some of the predominant species of a 

 recognized horizon disappearing at some localities, and giving place to others 

 of different characters. A glance at our table of distribution puts this in full 

 evidence. The coal beds of Morris, Colchester and Murphysborough, the two 

 first on the northeastern and northwestern, the last on the southwestern bor- 

 ders of the coal field of Illinois, are recognized, from all evidence, as repre- 

 senting coal No. 2, of the Illinois section, (in vol. 3, p. 6, of this Report) the 

 equivalent of coal 1 B, of the Kentucky Report. (2) 



Though the general character of the flora may be considered as the same, 

 we find, by comparison of the species at Murphysborough, eight peculiar spe- 

 cies ; five only in common with Colchester and Morris, and twelve in common 

 with Morris only, or altogether, eight species proper, and seventeen in common 

 with strata of the same horizon examined elsewhere in Illinois. Colchester 

 and Morris have been more carefully searched for specimens and are nearer to 

 each other. They have seventeen species in common, while Colchester has 

 nine species not yet found at Morris, and Morris has forty-four species, with- 

 out counting those of Blazon creek, which, as yet, have not been seen at Col- 

 chester. The coal of Duquoin, considered as No. 5, of the Illinois section, and 

 the only one from which as yet we have in Illinois and from a higher hori- 

 zon a number of fossil plants which can be used for comparison, has eleven 

 species proper, and seventeen in common with some or all of the other named 

 localities. Points of difference and identity are therefore as well marked for 

 this bed of coal as if it belonged to the same horizon as the others, and the 

 same differences are observable in the distribution of common or more pre- 

 dominant species. For example, Neuropteris flexuosa is most abundant at 

 Murphysborough, and has not as yet been found at Colchester and Morris, 

 where Pecopteris villosa and Callipteris Sullivantii are the predominant species; 

 and these are but rarely found, or not at all, at Murphysborough. On the 



(1) See, on this subject especially, Penna. Geol. Kept., p. 837; Amer. Jour, of Sci. and 

 Art, Nov. 1860. 



(2) All these strata are here marked according to the Illinois section. 



