62 



THE ARCHAEOPTERIS FLORA 



[cir. 



linear or filiform forked lobes as in the type species S. rigidum, 

 Lndw. (Fig. 34). 



Distribution. Middle Devo- 

 nian to Upper Carboniferous. 



Cephalopteris, Nathorst^, 

 1910 (Fig. 36). Axes branched, 

 branches opposite in distichous 

 pairs, each pair connate on one 

 side of the axis and decurrent. 

 Lower portions of branches 

 fertile. Sporangia in dense 

 spherical heads arising from 

 the decurrent base of each 

 lateral branch. Sporangia long, 

 ])ointed, dehiscing ? longi- 

 tudinally. Sterile foliage of 

 the ? Sphenopteridium type, 

 upper portions of branches 

 bearing small dichotomised 

 leafy segments. 



Distribution. Upper Devo- 

 nian, Bear Island. 



If Nathorst is correct in 

 correlating certain sterile leaf 

 segments (Fig. 36 (5)) with the 

 fertile main axes — a point on 

 which he expresses no doubt, 

 though to us there seems to be 

 no proof beyond mere associa- 

 tion — then this type is simply 

 a fertile Siihenopteridium, \ni- 

 less in its fructification it is 

 distinct from other members 

 of that genus, the fructifica- 

 tions of which are at present 

 quite unknown. For the 



Fig. 35. Spheuopteridium KeiUiaui, 

 Nath., from tlie Upper Devonian of 

 Bear Island. (Nat. size.) After Na- 

 thorst (1902). 



1 Nathorst (1902), first described under the name Cephalotbeca in tliat year. 



