UPPER PALEOZOIC FLORAS 147 



senting filicoid types of fructification. One-half of these genera 

 scarcely, if at all, survive the Pottsville. Three or four only outlive 

 the Allegheny. The Westphalian witnessed the maximum develop- 

 ment in Sphenopteris, Neuropteris, and Alethopteris, and of the great 

 Lycopod group. It is pre-eminently the stage of the Cycadifilices. 



Remarkable distribution of identical species. — The intercontinental 

 distribution of the Westphalian plants is probably less remarkably 

 uniform than is generally stated. The examination of the floras shows 

 minor differences between the floras of different basins, as, for 

 example, freshwater or marine basins in the same country, though 

 many of these differences disappear as additional material is collected. 

 Also different areas in the same basin, and, similarly, different hori- 

 zons in the same basin may show predominances of Lycopods, or 

 ferns, etc., or the apparent absence of certain genera. But as between 

 the larger provinces, and taking the flora as a whole, from continent 

 to continent, the number of genera not common, for example, to 

 Europe and America, is so small as to excite special interest. The 

 proportion of identical species is so large as to necessitate an extra- 

 ordinary lack of barriers to the freest migration. The flora of the 

 basin of Heraclea in Asia Minor' lends itself to ready correlation, 

 stage by stage, with three corresponding formations of the Pottsville 

 in the Appalachian trough; also, of the t^t, species reported by Zeil- 

 ler in a collection from the Westphalian of the Djebel-Bechar region 

 of Persia, 25 are present in the Pottsville of the Appalachian trough. 



The uniformity of distribution of the Westphalian flora complicates 

 the geographical question of its origin. Taking therefore as most 

 reliable the evidence of first appearances, we may note that Cheilan- 

 thites (including portions of Pseudopecopteris and Sphenopteris), 

 M.ariopteris, Eremopteris, Neuropteris, Alethopteris, and perhaps 

 Pecopteris, were more highly differentiated in America, though 

 Sphenopteris experienced a perhaps greater development in Austria 

 and Bohemia. In Europe the Lycopods appear to have had greater 

 advancement. Also, Cingularia, unknown outside of the freshwater 

 basins of Germany, and Lonchopteris, largely confined thereto, have 

 not yet been found in North America; while the unique genus 

 Neriopteris is still unknown in Europe. On the other hand, the rare 



I Jour. GeoL, Vol. IX (1901), p. 192. 



