v] 



RHACOPTERIS AND SPHENOPTERIDIUM 



61 



Rhacopteris, Schimper, 1872 (Fig. 33). Fronds pinnate or 

 dichotomously branched. Pinnules large, unsymmetrically 

 \\cdo-e-shaped, rhomboidal, typically entire or more or less 

 deeply lobed or divided longitudinally, with a radiating un- 

 symmetricfll nervation. Higher part of the frond sometimes 

 fertile, sporangia tufted, small, exannulate, globular. 



This genus is very rare in the Devonian, though it appears 

 to occur on that horizon in Germany. It is more characteristic 

 of the Lower Carboniferous. 



Distribution. Upper Devonian to Middle Coal Measures. 



Fig. 33. Rhacopteris furcillata, 

 (Ludw.), from the Upper Devo- 

 nian of Germany. (About ^ nat. 

 size.) After Potonie (1901). 



Fig. 34. Sphenopten'dium rigi- 

 dum, (Luaw.), from the Upper 

 Devonian of England and Ger- 

 many. (About I nat. size.) 

 After Potonie (1901). 



Sphenopteridium 1 , Schimper, 1874 (Figs. 34, 35). An indefin- 

 able generic name applied to a particular type of Sphenopterid 

 frond in which the pinnules are highly divided into very narrow 



1 This term is to be preferred to Rhodea, Presl, 1838, since that term is 

 preoccupied for Angiosperms (Rhodea, Endlicher, 1837; Rohdea, Roth, 

 1821). 



