OF THr: WEALDEN. 
•241 
SphcnnpfrrU .1 TanlcUi. 
Sphenopteri.s Mantelli. The form of this elegant 
fern is so remarkable, that it is easily recognised. 
Messrs. Stokes and Webb, from the shape of its 
frond, supposed that it resembled the plants of the 
genus Psilotum ; but from the disposition of the 
vessels in the ultimate segments, more nearly ap- 
proaching to that observable in those of the genera 
Trichomanes and Hpmenophpllum, and from the 
circumstance of all the divisions of the frond being, 
in the fossil, bordered by a decurrent membrane, 
those gentlemen formed a new sub-genus for its 
reception, which they named Hpmenopteris* M. 
* Geolog. Trans, vol. i. new series. 
R 
