NATHORSTIA. 145 



Genus NATHORSTIA, gen. nov. 



I propose to institute a new provisional genus of ferns for 

 the reception of certain specimens from the English Wealden, 

 which do not conform to the definitions of any known fossil 

 genera ; and, as some slight testimony to the palaeobotanical 

 labours of Dr. Nathorst, I have ventured to name the plants 

 after him. 



It will be seen that the specimens included under this genus 

 are imperfectly preserved frond fragments, and of such a kind 

 that it is impossible to arrive at any very satisfactory conclusion 

 as to their real nature. 



Two of the pieces are shown in PL VII. Fig. 5 and PL IX. 

 Pig. 2; these at first sight suggest portions of distinct species, 

 and at first I regarded them as such. 



On more careful examination, however, and after comparison 

 with other specimens, the differences become less pronounced and 

 seem to be rather apparent than real. 



In the absence of venation and fructification it is useless to 

 attempt a formal diagnosis of the genus; the characters will be 

 most conveniently indicated in the definition of the single species. 



Nathorstia valdensis, gen. et sp. nov. 



1871. ? Pecopteris Geinitzii, Schenk (in part), Paleeontographica, vol. xix. 

 p. 215, pi. xxix. figs. 2 and la. 



Type. Portions of sterile fronds. British Museum. PL VII. 

 Fig. 5. ; PL IX. Figs. 2 and 2a. 



Frond bipinnate (?), of slender habit, rachis thin but well 

 marked; pinnaa alternate or subopposite, long and of uniform 

 breadth; the small pinnules attached by the whole of the base, 

 margin entire or very slightly lobed, subdeltoid in shape, apex 

 obtuse ; some of the pinnules show faint traces of a midrib, but 

 no lateral veins. Fructification unknown. 



The specimen figured by Schenk from the neighbourhood of 

 Hannover as Pecopteris Geinitzii, Dunk., can hardly be referred 

 to that species as figured by Dunker. 1 On the whole it seems 



1 Wealdenbildung, pi. viii. fig. 3. 



