v] DOUBTFUL AND UNKNOWN GENERA 69 



which occurs widely and frequently in Australia, the so-called 

 Lepidodendron australe, is best referred to Leptophloeum , which 

 is wholly Devonian. Whitei has also recently concluded that by 

 far the greater number of the so-called American I^epidodendreae 

 belong in reality to Archaeosigillaria, occurring both in the Upper 

 Devonian and Lower Carboniferous though not in later rocks. 

 Lepidodendron appears to be wholly Carboniferous and Permian. 



Cordaites, Unger, 1850. The occurrence of Cordaites-like 

 leaves in Devonian rocks is very rare. One such is known from 

 England 2, though in a fragmentary condition, and others have 

 been recorded from Australia, but it cannot be said that the 

 evidence for the existence of Cordaites in Devonian times is at 

 present at all trustworthy. The evidence from the Devonian of 

 America is even less satisfactory. 



Distribution. ? Upper Devonian, Lower Carboniferous to 

 Permian. 



Genera unknown in the Devonian Rocks. 



Despite many assertions to the contrary in the older literature, 

 the following genera do not appear to be known in Devonian 

 rocks, or rather there are no trustworthy records of their occur- 

 rence in those beds. 



These genera were mostly well developed in Lower Carboni- 

 ferous times, as was also the genus Rhacopteris which is exceed- 

 ingly rare in the Devonian. Thus the Lower Carboniferous flora 

 is distinguished from that of the Devonian, by the presence of 

 the following genera, in addition to others common to the two 



formations. 



. ( Archaeocalamites 



" j Catamites (rare) 



Pteridospermeae [^^iantites 



°'' I Cardiopteris 



Filicales ' 



I Lepidodendron 

 Lycopodiales J Lepidophloios 



I Sigillaria (rare) 

 Cordaitales Cordaites (rare) 



1 White (1907). 



2 Arber and Goode (1915), PI. V, fig. 5. 



