378 FILICALES [CH. 



Japanese Wealden species, previously described by Geyler^ as 

 Thyrsopteris elongata, on the ground that, in addition to a 

 similarity in habit of the sterile fronds, the fertile pinnae 

 present a close agreement to those of the recent genus 

 Onychium. 



Onychiopsis Mantelli' (Brongn.). Figs. 278, D ; 280, A and B. 



The Japanese species Onychiopsis elongata may perhaps be 

 identical with this common Wealden fern which, as Fontaine 

 points out, should be called 0. psilotoides if the rule of priority 

 is to be observed irrespective of long usage. 



1824. Hynienopleris psilotoides, Stokes and Webb, Trans. Geol. Soc. 



[ii.], Vol. I. p. 423, PI. XLVi. fig. 7. 

 1828. Sphenopteris Mantelli, Brongniart, Hist. vdg. foss. p. 170, 



PI. XLV. figs. 3—7. 

 1890. Onychiopsis Mantelli, Nathorst, Denksch. Wien Akad. Vol. 



LVII. p. 5. 



Onychiopsis Mantelli may be defined as follows: — 



Frond bipinnate, ovate lanceolate, rachis winged ; pinnae approximate, 

 given oil' at an acute angle ; pinnules narrow, acuminate, with a single 

 vein ; the larger segments serrate and gradually passing into pinnae with 

 narrow ultimate segments. Fertile segments sessile or shortly stalked, 

 linear ovate, sometimes terminating in a short awn-like prolongation. 



The fertile segments (fig. 278, D) bear so close a resemblance 

 to those of species of Onychium that it would seem justii&able 

 to regard the plant as a member of the Polypodiaceae. This 

 fern is one of the most characteristic members of the Wealden 

 floras ; it occurs in abundance in the English Wealden, in 

 Portugal, Germany, Belgium, Japan, Bohemia, South Africa, 

 and elsewhere. A piece of rhizome figured from the English 

 Wealden^ is very similar to the creeping rhizomes of recent 

 species of Polypodiaceae. The English Wealden specimens 



1 Geyler (77) PI. xxxi. fig. 4. 



2 For synonymy, see Fontaine, in Ward (05) p. 155 ; Kichter (06) p. 6 ; 

 Seward (94) A. p. 41 ; (03) p. 5. 



3 Seward (94) A. p. 52. 



