BY THE REV. J. E. TENISON-WOODS, F.G.S., F.L.S. 103 



Dr. Feistmantel remarks that the form of the pinnae, the vena- 

 tion, and the thickness of the rachis all agree with Thinnfeldia. 

 He says that it might almost be identical with T. decurrens, Schenk, 

 a Rhsetic and Liassic plant, differing only in these points : — 1. The 

 rachis is thicker ; 2. The lower part of the base of pinnse not so 

 distinctly decurrent ; 3. The pinnse are thinner. He unites this 

 species with Pecopteris salicifolia, Morr. 



Found in the sandstones at Dubbo, where it is associated with 

 Thinnfeldia odontopteroides. The sandstones are without doubt 

 the same as the Hawkesbury sandstone, which I regard as an 

 aerial deposit. I have also recognized occasional fragments of this 

 Fern in ironstone. The differences in this species will appear 

 from the following diagnosis : — (Bi-pinnate ?) pinnse quite close, 

 nearly opposite, broadly lanceolate, broadly obtuse, the lower ones 

 shorter, attached by the whole of the base where it is only very 

 slightly constricted. Veins only faintly visible, but there are 

 traces of a costa in nearly all the pinnules which is evanescent. 

 Rachis very thick. 



While the venation is so indistinct we cannot be sure 

 that the fossil is a Thinnfeldia. It bears some resemblance 

 to T. indica, Feistmantel and more to T. decurrens, Schenk, 

 a Rhaetic and Liassic plant of Europe, differing only in the form 

 of the pinnae, which are more obtuse. I think I have also 

 recognized varieties of this Fern in ironstone nodules, which have 

 evidently been derived from the Hawkesbury rocks by weathering. 

 The decomposition of the plants has given rise to a nucleus by 

 deoxidizing the ferric oxides in the felspars contained in the sand- 

 stone, as stated in the paper on the Hawkesbury sandstone in the 

 Roy. Soc. N. S. Wales for 1882. A careful examination of these 

 nodules generally manifests some fragments of plant remains. 



Thinnfeldia odontopteroides. — Morris (1845) Physical Des. 

 N.S.W., Strzelecki, as Pecopteris p. 249, pi. vi., figs. 2, 3, 4 ; 1847, 

 Gleichenites odontopteroides, M'Coy, A. and M. Nat. History, vol. 

 xx, 2nd Ser., p. 147, 1850, Idem. Unger., Genera et species plant, 

 fossilium, p. 208 ; 1869, Cycadopteris (?) odontopteroides, Schimper, 

 Trait, de Paleont. vegetale, vol. i., p. 488 ; 1869, Alethopteris (?) 



