572 



MR ROBERT KIDSTON ON 



Diagrammatical] y, the rarity or frequency of a species might be represented thus ; — 



Coal Measures. 



Alethopteris Jonahitica, Schl., sp., 

 Alethopteris Serlii, Bgt., sp., 



Pecopteris arborescens, Schl., sp., 



Stigmariaficoides, Sternb., sp., . 



Table I. 



Comparative Table of the Fossil Plants of the Upper Pennant, South Wales Coal 

 Field, with those of the Upper, Middle, and Lower Coal Measures. 





Upper 

 Pennant. 



Upper 

 Coal Meas. 



Middle 

 Coal Meas. 



Lower 

 Coal Meas. 



Splienopteris neuropteroides, Boulay, sp., 

 Neuropteris flexuosa, Bgt., . 



„ Sclteuclizeri, Hoffm., 

 Pecopteris Miltoni, Artis, sp., 

 Alethopteris lonehitica, Schl., sp., 



,, Serlii, Bgt., 

 Sigillaria tessellata, Bgt., 

 Stigmaria ficoides, Stbg., sp., 







XXXXXXXX 



XXXXXXXX 



X X X X X X 



XX XX 



Analysis of Table I. 



Of the 8 species of fossil plants collected from the Upper Pennant of the South 

 Wales Coal Field, all occur in the Upper Coal Measures : of these, 2 are characteristic 

 of that horizon, as far as at present known, viz., Splienopteris neuropteroides and 

 Neuropteris flexuosa. 



Six of the Upper Pennant species occur in the Middle Coal Measures, all of which 

 have previously been met with in the Upper Coal Measures, as mentioned above. 



Four of the Upper Pennant species occur in the Lower Coal Measures, but all of 

 these occur also in the Upper Coal Measures. 



All the species found in the Upper Pennant of South Wales occur at other localities 

 in Britain. 



This analysis of the Upper Pennant species shows very evidently that these rocks 

 must be referred to the Upper Coal Measures as developed in Britain, though represent- 

 ing their basement beds. 



The absence of Pecopteris arborescens, Pecopteris oreopteridia, and allied forms, 

 with the exception of Pecopteris Miltoni, is very remarkable. I saw a fragment which 



1 I have seen a somewhat similar mode of tabulation adopted by a recent palseontological writer, but I cannot 

 remember by whom. 



