ONrcHioPsis. 43 



it would "probably be a Sphenopteris " in tbe system of Brong- 

 niart. They proposed the name Symenopteris psihtoides. The 

 same figure reappears in Mantell's " Illustrations of the Geology 

 of Sussex " under the original name. The species Sphenopteris 

 Mantelli is first mentioned by Mantell ' in a quotation from a letter 

 received by him from Brongniart, who proposed that the name 

 Symenopteris psilotoides should be replaced by the more suitable 

 designation Sphenopteris Mantelli. 



Brongniart ^ includes the species in his Prodrome, and gives the 

 first diagnosis in the Histoire' : — 



" S. foliis bipinnatifldis, pinnis approximatis virgatis fastigiatis, 

 pinnulis obliquis, omnibus integris uninerviis, angustis, cuneatis, 

 apice oblique trunoatis et subemarginatis ; parte exteriori longius 

 producta." 



Since 1828 different writers have added to or variously modified 

 Brongniart's definition ; without quoting any of these we may 

 substitute a definition of the species founded on the exceedingly 

 good material in the National Collection. 



Frond tripinnate, ovate lanceolate, rachis winged and prominent ; 

 pinnae lanceolate, alternate, approximate, given off from the main 

 rachis at an acute angle. Pinnules alternate, narrow, lanceolate 

 acuminate, uninerved, of nervation type Coenopteridis ; ^ the larger 

 ones serrate and gradually passing into pinnae with narrow ultimate 

 segments. 



Fructification in the form of sessile or shortly stalked linear 

 ovate segments with rugose surfaces, and terminating usually in 

 a very short awn -like apical prolongation. 



The specimen figured by Mantell in 1827' (pi. iii. fig. 6) may 

 belong to this species, but the figure represents a number of 

 detached fragments which it is impossible to refer with much 

 certainty to any species. Mantell's Sphenopteris Sillimani^ is very 

 possibly a badly preserved piece of an Onychiopsis Mantelli frond. 

 Carruthers,' in his account of the Cretaceous plants in Dixon's 



1 Illust. Geol. Sussex, p. 55. 



* Prodrome, p. 60. 



' Hist. veg. foss. p. 170. 



" Luerssen, in Eabenhorst's Krypt. Flora, vol. iii. p. 11. 



^ Illust. Geol. Sussex. 



» Geol. S.E. England, p. 239. 



' Geol. Sussex, p. 282. 



