12 THE TWO FLORAS [CH. 



associated with Psilophyton (? the Palaeophycus gracilis or 

 Noeggeratkia bifurca of Ludwig). 



Bohemia. The Middle Devonian flora of Barrande's horizon 

 h 1 in Bohemia 1 consists almost entirely of members of the 

 Psilophyton flora, including Arthrostigma, Hostimella and 

 probably Psilophyton, with Pseudosporochnus, Barrandeina, 

 Protolepidodendron and Thursophyton. The only more modern 

 types are a doubtful example of Sphenopteridium and Archaeo- 

 sigillaria (the Protolepidodendron S chary anum of Krejci and 

 Potonie). 



Norway (Roragen). The probably Lower Devonian flora of 

 Roragen 2 comprises Arthrostigma, Psilophyton, Hostimella, 

 Aphyllopteris, and Sporogonites, without any more modern types. 



Norway (Western). The possibly Middle Devonian of Western 

 Norway 3 includes Spiropteris, Aphyllopteris, Thursophyton, 

 Broggeria, and possibly Barrandeina, associated with the more 

 modern types, Psygmophyllum and Hyenia. 



Russia. From the Upper Devonian of the Donetz Basin 4 are 

 known two species of Archaeopteris, examples of an isolated 

 fructification (Dimeripteris) with a species of Sphenopteris and 

 possibly a Lepidodendron. No members of the Psilophyton flora 

 occur. 



Bear Island (Arctic Regions). We find here a very interesting 

 Upper Devonian flora of the Archaeopteris type, including 

 Archaeopteris Roemeriana, (Goepp.) and other species, Bothro- 

 dendron Kiltorkense, (Haught.), species of Sphenopteridium, 

 Sphenophyllum and Stigmaria associated with the rare types 

 Pseudobornia ursina, Nath., and Cephalopteris mirabilis, Nath. 5 . 

 No archaic types have been recognised. 



Ellesmereland (Arctic Regions). From the Upper Devonian 

 of Ellesmereland 6 two species of Archaeopteris (A. Archaetypus 

 and A. fissilis which both occur in Russia) are associated with 

 a Sphenopteridium. 



Spitzbergen (Arctic Regions). In rocks assigned to the Upper 

 (or possibly the Middle) Devonian of Spitzbergen 7 , we find a 



1 Potonie and Bernard (1904); Stur (1881). 



2 Halle (1916); Nathorst (1913). 3 Nathorst (1915). 

 * Schmalhausen (1894). 5 Nathorst (1902). 

 6 Nathorst (1904). 7 Nathorst (1894). 



