12 THE TWO FLORAS [ch. 



associated T^ith Psilophyton (? the Palaeophycus gracilis or 

 Noeggerathia bifurca of Ludwig). 



Bohemia. The Middle Devonian flora of Barrande's horizon 

 ^ 1 in Bohemia^ 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 Scharyanum of Krejci and 

 Potonie). 



Norway (Roragen). The probably Lower Devonian flora of 

 Roragen ^ comprises Arthrostigma, Psilophyton, Hostimella, 

 Aphyllopteris, and Sporogonites, without any more modern types. 



Norway (Western). The possibly Middle Devonian of Western 

 Norway^ includes Spiropteris, Aphyllopteris, Thursophyton, 

 Broggeria, and possibly Barrandeina, associated with the more 

 modern types, Psygmophyllum and Hyenia. 



Russia. Froni the Upper Devonian of the Donetz Basin* 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 

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

 No archaic types have been recognised. 



Ellesmereland (Arctic Regions). From the Upper Devonian 

 of Ellesmereland^ 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', we find a 



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



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

 4 Schmalhausen (1894). = Nathorst (1902). 

 6 Nathorst (1904). ' Nathorst (1894). 



