EOCENE FERNS. 



43 



along the base, wliicli forms almost a right angle with the stipes, and at least four 

 inches in length. The texture is exceptionally membranous, the sori, where the 

 lobes overlap each other in places, being distinctly traceable through it ; this character 

 removes it from Pteris, in which genus it might otherwise possibly have been placed. 

 The stipes was glabrous, rigid, slender, and must have been at least three times longer 

 than the portion preserved. The veins are very fine and distinct, and anastomose 

 copiously, but become less conspicuously reticulated towards the margin, as seen in the 

 enlargements, PI. X, fig. 6 a ; PI. XI, fig. 4. The sori form long linear patches Uf)on 

 both edges, but do not extend to the extremities of the lobes. The specimen, PI. II, 

 fig. 5, is probably a small barren frond of the same species. Only the outline is 

 preserved, which is suborbicular, with margin entire. 



The slender stipes, membranous texture, and marginal sori are characters only com- 

 bined in Adiantum and Liudsaya. In the latter genus L. sagittata possesses simple 

 fronds and is not very inferior in size ; but it is in the section of Adiantum with anasto- 

 mosing veins, Heioardia of J. Smith, that we find the nearest resemblance to it. H. 

 Wilsoni, although not possessing perfectly simple fronds, sometimes has its pinnae almost 

 all united in a single trilobed terminal pinna, approaching the fossil species in dimen- 

 sions. Even the nearest living species, however, differ very widely from it, and it thus 

 appears to be one of the few Tertiary Perns that have become completely extinct. We 

 are not acquainted with any fossil species with which to compare it. 



We had frequently noticed fragments of a very membranous Fern with anastomosing 

 venation, and two of these had been figured without any clue as to the form of the leaf, 

 before the magnificent specimen on PI. XI had come to light. Our attention was called 

 to it by a lady, who found it in a small concretion of white clay near the base of the 

 black clays, in the leaf-beds nearest to, and on the west side of Bournemouth Pier. The 

 other fragments were found in the same beds. 



(f) Gleicheniacece. 



Genus. — Gleichenia. 



(Sub-genus. — Mertensia.) 



Gleichenia Hantonensis {WanUyn). Plate VI and Plate X, figs. 2, 3, 4. 



Mertensites Hantonensis and M. crenata, fVankhjn. Annals and Magazine of 



Natural History, vol. iii, pi. i. 1869. 



G.fronde gracili siipitata dlchotoma ; stijjite scandente ; cirrhis ahbreviatis uncinatis ; 



