ONYCHIOPSIS. 43 
it would “probably be a Sphenopteris”’ in the system of Brong- 
niart. They proposed the name Hymenopteris psilotoides. 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 
Hymenopteris 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* :— 
‘‘§. foliis bipinnatifidis, pinnis approximatis virgatis fastigiatis, 
pinnulis obliquis, omnibus integris uninerviis, angustis, cuneatis, 
apice oblique truncatis 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 ; 
pinne 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 pinne 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° (pl. iil. 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 Tllust. Geol. Sussex, p. 55. 
2 Prodrome, p. 50. 
3 Hist. vég. foss. p. 170. 
4 Luerssen, in Rabenhorst’s Krypt. Flora, vol. iii. p. 11. 
5 Tllust. Geol. Sussex. 
§ Geol. S.E. England, p. 239. 
7 Geol. Sussex, p. 282. 
