672 PROFESSOR A. C. SEWARD ON 



of ground-tissue (cortex) shown at A'. In spite of the unsatisfactory condition of the 

 specimen, I feel little doubt as to the solenostelic structure of the stem. Attempts * to 

 obtain a longitudinal section were unsuccessful, nor was it possible to cut a transverse 

 section through the base of a petiole, which would probably have shown the solenostele 

 interrupted by the departure of the leaf-trace. 



The type of stele which I believe to be illustrated by the Culgower rhizome, namely 

 a hollow cylinder or solenostele, is met with in several genera of recent ferns, notably 

 in the genus Dipteris. The resemblance to this fern is especially significant in view of 

 the abundance of Hausmannia leaves in the same rocks, a Mesozoic genus which is 

 almost certainly very closely related to recent species of Dipteris. The habit of 

 Hausmannia rhizomes as described by Richter t agrees with that of the fossil stem, and 

 both resemble closely the rhizome of Dipteris. A transverse section of a rhizome of 

 Dipteris bears a striking resemblance to that of the Culgower specimen in the structure 

 of the cortical and axial ground-tissue and, making allowance for contraction of the 

 vascular tissue previous to petrifaction, the form and size of the stele are very similar. 

 While recognising the necessity of describing Rhizomopteris Gunni as a rhizome of 

 uncertain position, I am inclined to regard it as belonging to one of the species of 

 Hausmannia. 



Sphenopteris, Brongniart. 



Sphenopteris onychiopsoides sp. nov. (PI. II. figs. 22-24A ; PI. VI. photo. 10.) 



1871. Pecopteris Geinitzii, Schenk, Palxontographica, Ed. xix. p. 215, pi. xxix. figs. 2, 2a. 



The fragmentary specimens on which this species is founded were at first sight con- 

 sidered to be identical with Onychiopsis Mantelli (Brongn.), a characteristic Wealden 

 fern, but a closer examination revealed certain differences which convinced me that the 

 resemblance is only superficial. The best specimen is that reproduced in Photo. 10, PI. 

 VI. ; a comparatively slender rachis gives off several linear pinnae bearing narrow oval 

 segments terminating in a lanceolate or rather blunt apex. The longest pinna, 2 - 8 cm., 

 tapers very gradually to an acuminate distal end ; the veins are not visible. Fig. 22, 

 PI. II., shows the apex of a similar frond in which the linear pinnae pass into simple 

 apical segments. The obscure example represented in fig. 23 is especially close to 

 Onychiopsis in appearance, but it is probably a badly preserved piece of a frond of the 

 same species as fig. 22. The piece of pinna shown in figs. 24, 24A illustrates the uniform 

 breadth of the branches of the rachis, as also the basal constriction of the pinnules, which 

 are more acutely terminated in this specimen than in that shown in figs. 22, 22A. 



Sphenopteris onychiopsoides is characterised by the elongated narrow pinnae, by the 

 oval, basally constricted, ultimate segments continuous with one another on the edge 

 of the axis. The venation, which is seldom preserved, consists of a midrib giving off 



* The whole of the small piece of stem was destroyed in abortive attempts to obtain sections. Only two com- 

 plete (transverse) sections were made, 

 t Richter (06). 



