DICHOPTERIS. 183 



Genus DICHOPTERIS, Zigno. 



[Mem. Instit. Veneto, vol. xii. p. 217, 1864.] 



This genus is defined by Zigno as follows: 



"Frons bipartita, bipinnata, rachide primaria, crassa, striata. 

 Pinnae liberse, pinnatifida?, alternse, vel suboppositse. Pinnuhe 

 coriacese iutegerrinia3, saspe basi angustataB, in rachides alatas 

 decurrentes. Nervi agquales pauci, simplices, interduui furcati, 

 e rachide seriatim orti, ad apicem marginemve pinnularum 

 flabellatim excurrentes. Sori rotundi, prominuli, sparsi. Capsulse 

 (Sporangia) ovato-globosaB, sessiles, vel subsessiles, annulo complete 

 cinctse. Filices elasticas, rachide crassa bipartita, facie Gleichenia- 



cearum." 



Zigno's genus is classed by Solms-Laubach l with Nilssonia, 

 Thinnfeldia, and others, which " have been shifted backwards 

 and forwards by different authors from cycads to ferns, and from 

 ferns to cycads." In looking over the references to Dichopteris 

 by various writers, we find a considerable difference of opinion, 

 both as regards the necessity for such a generic designation, in 

 distinction to the much older genus Pachypteris of Brongniart, 

 and as to the affinity of the plants described under this name. 

 Schimper, in the first volume of the Trait, pal. veg.^ includes 

 Dichopteris under Pachypteris, and remarks that it is "impossible 

 to doubt the identity of the two genera"; in the third volume 3 

 of the same work, he includes the former among the ferns as an 

 independent genus. Saporta includes some species of Dichopteris 

 in his genus Scleropteris 4 ; e.g. the two plants originally described 

 by Phillips from the Lower Sandstone and Shale of the Yorkshire 

 Coast as Sphenopteris lanceolata, 5 Phill., and Neuropteris lavigata? 

 Phill., but the nature of these species has been a matter of 



1 Fossil Botany, p. 87. 



2 p. 492. 



3 p. 490. 



4 Saporta, Pal. Fran^. vol. i. p. 364. 



5 Phillips (A. 2), p. 200, pi. x. fig. 6. 



6 Ibid. p. 201, pi. x. fig. 9. 



