^g^"' ] Chkpman, Geological History of Australian Plants. 149 



containing Thinnfddia, Sphenopteris, Tceniopteris {Macro- 

 tceniopteris), Odontopteris, Sagenoptcris, Schizoneura, and a 

 branchiopod, Estheria. 



One of the striking features of Sydney's buildings is the 

 general use that is made of the Hawkesbury sandstone. This 

 is worked as a freestone, and from its weathered structure, 

 which can be well seen on the time-worn cliffs in the harbour, 

 it distinctly shows the cross-bedded nature of the sand-mounds 

 of which it is formed. This cross-bedding is seen in all dune- 

 formations, recent and geologically ancient ; but, notwith- 

 standing this, we find certain text-books still attempting to 

 teach an invariable rule that it is due to rippling under water. 

 In some cases, of course, the fine-bedded current stratum is 

 due to sub-aqueous action, and possibly even on occasion in 

 the Hawkesbury sandstone, but in the writer's opinion this 

 was subordinated to wind action. 



The handsome fern-like plant, Thinnfeldia odontopteroides, is 

 a typical fossil of this stage. It is remarkable that until quite 

 recently no reproductive organs were found in Australian 

 specimens of this genus.* Prof. Seward says, in reference to 

 Thinnfeldia f : — " It is by no means improbable that many 

 of the species referred to this genus are closely allied to Palaeo- 

 zoic Pteridospermi," and further suggests that " search should 

 be made for fertile specimens or for evidence as to the associa- 

 tion of seeds with Thinnfeldia fronds." { It is, therefore, with 

 no little interest that palsobotanists welcome the description 

 by Dr. A. B. Walkom, of Queensland, of fertile fronds of T. 

 Feistmanteli and T. lancifolia, discovered by Mr. B. Dunstan 

 at Denmark Hill, Ipswich. § These interesting specimens are 

 so well preserved as to exhibit the cell-structure of the 

 sporangium wall ; the latter have no apparent annulus, and 

 thereby show some affinity to the tropical ferns of the family 

 MarattiacecB. 



Plant remains are numerous in the Wianamatta shales, one 

 of the most interesting being the large-leaved forerunner of 

 the Jurassic Tceniopteris — Macrotcaniopteris. This latter genus 

 or sub-genus has also occurred || in the Triassic sandstone at 

 Bald Hill, near Bacchus Marsh. A careful examination of 

 the type of Tceniopteris Sweeti fails, however, to reveal any 

 distinction from T. {Macrotceniopteris) wianamattce . Other 



* Raciborski, in 1894, figured a fertile specimen of T. rhomboidalis, 

 showing sori but no definite sporangia, from the Jurassic of Poland. 



t " Fossil Plants," vol. ii., 1910, p. 537. 



top. cit., p. 538. 



§ Queensland Geol. Surv., publ. No. 257, 1917, pp. 15, 16, 18, pi. i., fig. 

 3 ; pi. iii., fig. 3; text fig. 5. 



IlProc. R. Soc. Vict., vol. x., part 2, 1898, p. 285. 



