90 GENERA OF UNCERTAIN POSITION [CH. 



the material from a botanical point of view. Failing reproductive 

 organs or petrified specimens some useful evidence might be 

 afforded by an examination of the cuticular structure of well 

 preserved leaves. 



RHIPIDOPSIS. Schmalhausen 



Schmalhausen 1 instituted this genus for large petiolate oval 

 leaves from the Permian rocks of the Petschora district, charac- 

 terised by the division of the lamina into several obcuneate or 

 obovate segments closely resembling in their form and venation 

 some forms of Psygmophyllum especially P. Hay clem 2 . We have 

 no definite information as to the systematic position of the parent- 

 plant; the genus has usually been regarded as a representative 

 of the Ginkgoales on the ground of similarity in the leaves, but 

 while admitting that a relationship between Rhipidopsis and 

 Ginkgo is not improbable it is the safer course to regard Rhipidopsis 

 as a genus of Gymnosperms of uncertain affinity. Schmalhausen 

 attributes to Rhipidopsis some Samaropsis seeds 3 found in associa- 

 tion with the leaves, and Kurtz 4 states that he has found leaves 

 and 'fruits' in the Argentine. No proof of any connexion between 

 leaves and seeds has so far been discovered. The genus is recorded 

 from Russia, South America, and India from strata that are 

 Permian or approximately Permian in age. 



Rhipidopsis (fig. 670) is distinguished from Psygmophyllum by 

 the presence of d petiole and from most, forms of that genus by the 

 deeper dissection of the lamina, as also by a more pronounced 

 difference in form and size between the several segments of the 

 lamina. Zeiller 5 has drawn attention to a close resemblance 

 between Rhipidopsis and a specimen figured by Schmalhausen 

 from the Artinsk Permian beds as Psygmophyllum expansum?. 



Rhipidopsis ginkgoides Schmalhausen. 



The type-species (fig. 670) is characterised by the large size 

 of the leaves which, according to Schmalhausen 7 , may reach a 



1 Schmalhausen (79) A. p. 50, Pis. vi., vin. 



2 See p. 86, fig. 668. 



3 Schmalhausen (79) A. PI. vm. figs. 911. 



4 Zeiller (96) A. p. 467. 5 Ibid. p. 471. 



6 Schmalhausen (87) PI. ra. fig. 10. 



7 Schmalhausen (79) A. p. 50, Pis. vi., vm. 



