564 



PTERIDOSPERMS, ETC. 



[CH. 



probably not generically identical with the Irish and Arctic 

 species. The dichotomous branching of the rachis in A. Tscher- 

 maki and A. Dawsoni is a feature unknown in Arehaeopteris. 



Fio. 369. 



Arehaeopteris hibemica. Fertile pinna. Dublin Geological 

 Survey Museum. (Keduced. After Kidston.) 



B. A. hibemica. Pinnule. (Slightly enlarged. After Carruthers.) 



C. A. hibemica. Base of petiole. (Dublin Museum. After Kidston.) 



D. A. archetypiis. Base of petiole : Ellesmere Land. (After 

 Nathorst. J nat. size.) 



E. A. fissilis. Sporangia. (Slightly enlarged. After Schmal- 

 hausen.) 



F. A. fissilis. Sterile pinnule. Ellesmere Land. (Slightly en- 

 larged. After Nathorst.) 



G. A.Jimbriata. Bear Island. (After Nathorst. f nat. size.) 

 H. Arehaeopteris sp. 



size.) 



Ellesmere Land. (After Nathorst. J nat. 



In the absence of fertile pinnae the separation of Arehaeopteris 

 from Rhacopteris is by no means easy. 



