514 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



strued to indicate that this region was probably on the eastern bor- 

 der of the Oigantopteris province. 



The Oigantopteris flora (early Permian) very probably preceded the 

 development of the Gangamopteris flora in southern Asia. Did the 

 Oangamopteris (Permian) flora, which came by an Antarctic route to 

 southern South America, ever follow the Gigantopteris flora by the 

 northern route into western North America? The extension of the 

 eastern Asiatic province to the western border of this continent in 

 Gigantopteris time, and the reported presence of Glossopteris, a sur- 

 vivor of the Gangamopteris flora in the Mesozoic of western Mexico, 

 makes it seem not impossible that the Gangamopteris flora also may 

 have reached North America. In view of the almost total lack of 

 paleobotanical knowledge concerning the Pennsylvanian and Per- 

 mian rocks of all North America west of the Rocky Mountains, it 

 will readily be recognized that the Gangamopteris flora may be present, 

 though it may be a long time before paleontological exploration will 

 have been carried so far as to unearth its remains. 



EXPLANATION OF PLATES. 

 Plate 43. 



Gigantopteris americana. 



Young frond showing nearly equal division and slight constriction at the point of 

 dichotomy. The border of the lamina in this specimen is seen to be sometimes con- 

 cave, sometimes convex, opposite ends of the secondary nerves. 



(Cat. No. 34070, U.S.N.M. Photographed in natural size.) 



Plate 44. 

 Grigantopteris americana. 



Fragment of leaf in which the incomplete lamina appears to be gradually narrowed 

 downward, becoming slightly lobate at the same time. The basal portion of the 

 lamina, which is slightly macerated, has been destroyed. 



(Cat. No. 34069, U.S.N.M. Photographed in natural size.) 



Plate 45. 

 Gigantopteris americana. 



Portion of large leaf showing the union of two lobes far above the point of dichotomy, 

 with very little constriction at the sinus. The border is seen to be convex opposite 

 the secondary nerves in the upper part of the division on the right. The secondary 

 nerves are opposite to alternate. 



(Cat. No. 34071, U.S.N.M. Figure reduced to | natural size.) 



Plate 46. 



Gigantopteris americana. 



Fig. 1. — Fragment of a relatively slender lobe showing the Goniopteroid aspect of 

 the margin and nervation. The sutural nerves are evident in this young pinna, and 

 the border is concave opposite the ends of the secondary nerves, probably as the 

 result of slight shrinkage. 



