102 G. F. MATTHEW ON THE OEGANIC RPMAINS OF THE 



2. Genera of the Pre- Carboniferous land plants of Northeastern America. 



To bring more clearly into view the relationship of the plants of the Little R. Group 

 with those above and below it, the author has made the following tabulated statement of 

 the genera. The table is compiled chiefly from the writings of Sir J. "W". Dawson,' and from 

 its sixty genera scattered through the several members of the Devonian system and the 

 Little R. Group (including two from the Silurian) a rough estimate may be arrived at of the 

 relation of the plants of the Little River Group to the floras of other parts of Northeastern 

 America. In noting the related or identical genera the writer has followed the indications 

 given by Sir "William and by Leo. Lesquereaux in his Coal Flora of Pennsylvania, and for 

 the Upper Carboniferous by Fontaine and "White's work on the flora of "West Virginia of that 

 age. A more complete view of the range of the genera might be given, but the references 

 of these authors are suflacient for the purpose in view. 



In making these comparisons the author has omitted from consideration the species 

 based on the woody tissues of plants, as only those of the Middle Devonian have received 

 much attention. 



A fact that strikes one looking over this list of genera is the large number of species, 

 collected almost all from one locality, that form the contents of the fifth column, the flora of 

 the Little R. Group, which thus exceeds in variety all the others, older than the Carbonifei'ous. 

 "We also notice a regular graded increase in the number of genera (omitting the fossil woods), 

 from the Silurian onward to the fifth column where it ceases ; but we also note a marked 

 decrease in the sixth column owing to the poverty of the Lower Carboniferous flora in this 

 region of northeastern America. The most remarkable feature of the table is the survival 

 to Middle Carboniferous times of so large a number of the genera of the Little River flora, 

 amounting to sixty-four per cent of the whole of this flora, leaving only about a fifth of the 

 survivals as derivatives from the other floras. This would not be so remarkable if one could 

 place the Little River as a Lower Carboniferous flora, but as we are driven by the stratigra- 

 phical requirements to place it much lower in the geological scale (as shown by my former 

 article on this group), it shows that comparisons of this kind give but little help in determin- 

 ing the geological age of extinct land floras. 



"We are, therefore, driven to find some other means of applying the data of this table 

 for the purpose of determining geological horizons, and especially that of the Little River 

 group. On running the eye down the fifth and sixth columns it will be observed that 

 several genera found in the Lower Carboniferous, survivals from earlier times, did not live 

 on to the time of the coal-measures, these were Psilophyton, Bornia, Leptophleum, Lepido- 

 dendron,' Aneimites, Archieopteris, Ptilopliyton, Megalopteris. Some of these have a wide 

 range in the Pre-Carboniferous floras, and all of them are only known as ancient types. All 

 of these genera, except Leptophleum and Archseopteris, are found in the Little River group, 

 and proclaim its antiquity. 



' Flora of the Devonian period in nortlieastern America. 

 New tree ferns and other fossils from the Devonian. 



Further observations on the Devonian plants of Maine, Gaspé and N. York. 

 Fossil plants of the Devonian and Silurian formations of Canada. 



'' I here depend on the authorities cited above ; some of these genera no doubt run higher, but perhaps no 

 representatives of the early species. 



