RANGE OF MISSOURI SPECIES IN BRITISH COALFIELDS. 299 



proximate equality of the percentages in this table is due; but the Upper 

 Coal Measures of Great Britain contain many higher forms, such as Pe- 

 copteris polymorpha, Brongn., P. miltoni, Artis, and P. pteroides, Brongn., 

 besides the P. arborescens, Brongn., and other higher forms, which are not 

 present in our flora, while the general character of the plants of that 

 division is of a rather higher order. In brief, considering this important 

 circumstance on the one hand as well as the relations evidently later 

 than the Middle Coal Measures on the other hand, we may, it would 

 seem, safely conclude that the lower coals in the vicinity of Clinton are 

 certainly not older than the Middle Coal Measures of Great Britain, but 

 most probably younger, or that they are presumably as late as the Transi- 

 tion series,* whose flora, though as ) 7 et but little exploited, shows rela- 

 tively the closest affinities. It is quite possible, however, that the depo- 

 sition of our flora was even so late as the sedimentation of the basal por- 

 tion of the Upper Coal Measures of the British coalfields. 



STRATIGRAPHIC RANGE IN THE FRANCO-BELGIAN FIELD. 



To indicate in part the relation of our flora to those of Continental 

 Europe we may take into comparison, as typically illustrating the suc- 

 cession of plant life in Europe during this portion of Carboniferous time, 

 the series developed in the Valenciennes basin of the Franco-Belgian 

 coalfield, the floras of which have been elaborated with masterly thor- 

 oughness and skill by Rene Zeiller. f The distribution of the identical 

 Henry County plants as well as of the related species X in the three pale- 

 ontological zones, into which M. Zeiller finds the Valenciennes series 

 (Houlller Moyeii) to be divided, is shown on the accompanying table. 



The limit of space precludes in this place any remark on either the 

 paleontological characters of the three zones or the surprising degree of 

 similarity between the Missouri flora and that of the upper zone of the 

 Valenciennes series. A short inspection of the tabular columns shows 

 that while only a relatively small percentage of our species is present 

 in the lower zone, over one-half are found in the Middle (Anzin-Meur- 

 chin) zone, but the conspicuous feature is the occurrence of 24 or 25 of 

 the 26 identical species in the Upper (Bully-Grenay) zone. The evi- 

 dence afforded by the distribution of the species needs only to be sup- 

 plemented by a review of Zeiller's profuse and admirably executed 

 figures of the species in the Upper zone to carry the conviction that in 



*The New Rock and the Vobster series of the Bristol and Somerset coalfield and the " Lower 

 Pennant" of the South Wales coalfield. 



t Etudes des gites mineraux de la France. Bassin houiller de Valenciennes. Description de la 

 Flora Fossile, par R. Zeiller. Ministere d. travaux publics, etc., Paris, text, 1888, pp. 1-731, quarto ; 

 1886, atlas, pis. i-xciv, quarto. 



JThe related species (parenthesized), the distribution of which is given, is written subjacent to 

 the respective American species. 



