288 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 14. 



artificial assemblages, I consider generic identity in that tribe of plants 

 as perfectly unimportant with reference to geology. 



Of the fossils noticed in this memoir, the obscure impressions num- 

 bered 1 2 and 1 3 are those which bear most resemblance to forms of 

 the true carboniferous system ; but I thmk it quite unsafe to draw 

 any conclusion from specimens so imperfect. The stem numbered 14, 

 if it were, as I conjecture, a part of a Conifer, is as likely to have be- 

 longed to the triassic series (in which Conifers are numerous) as to 

 any other. 



On the whole, then, as far as the evidence from vegetable remains 

 is concerned, we may say with tolerable confidence that the Richmond 

 coal-field belongs either to the triassic or to the Jurassic series ; and 

 it might be referred with almost equal plausibility to either. At any 

 rate, there can hardly be a doubt that it is of later date than the true 

 coal-measures. All over the continent of North America, from Nova 

 Scotia to Alabama, wherever the great carboniferous system has been 

 examined, it has been found to be characterized by a most remarkable 

 similarity, and almost a uniformity, in its vegetable productions. 

 Here, on the other hand, we find an assemblage of plants, of which 

 all that occur in a determinable or intelligible state differ essentially 

 from those of the carboniferous system, and of which some are iden- 

 tical with, and others closely resemble, European fossils of the secon- 

 dary series. 



DESCRIPTION OF THE PLATES. 



Plate X. 



Neuropteris linncecefolia. 

 b. A single leaflet, slightly magnified. 



Plate XI. 

 Fig. 1. Pecopteris bullata. 



\ a. k single leaflet, upper side, slightly magnified. 



1 b. Some of the pustular elevations occasioned by the fructification, magnified. 



1 c. A leaflet, lower side, slightly magnified. 

 Fig. 2. Filicites fimbriatus. 



2 a. A portion slightly magnified. 



