BY A. B. WALKOM. 151 



they are lightly referred to tlie genus. Dr. Slopes (1918, p. 230) differs from 

 my determination of them as Otoaamitea, but does not suggest to what genus 

 she considers they should be referred. 



The rocks in which these species occur are all referred to the Walloon 

 Series or its ecjuivalents. which are of undoubted Jurassic age. 



The Western Australian oecurrenees of Otozamites are confined, so far as 

 is known, to the neighbourhood of Mingenew, and Madinganarra, to the north 

 of Derby. The only published records are those of Arber (1910), about three 

 miles south of Mingenew, and A. Gibb Maitland (1919. p. 41) near Derby, in 

 addition to those described in the present paper from about three miles north 

 of Mingenew. The species comjirise (>. Becliei, U. Feistmanteli and (). benga- 

 lensis from the neighbourhood of Mingenew, and 0. sp. from Madinganarra. 



Ml-. A. Gibb Maitland, in his Summary of the Geology of Western Aus- 

 tralia (1919, p. 41), records thii occurrence of the genus in the north-west of 

 Australia thus: — 



"Di-. H. Basedow obtained in 1916 several impressions of Mesozoie ferns 

 in a yellowish ai'gillaceous sandstone or gTit met with in a well at Madin- 

 ganaiTa, near Point Torment, to the north of Derby in King Sound in the 

 Kimberley Divisi<m. The specimens have been determined by the late Mr. 

 R. Etheridge, Jun., as Otozamiies, together with stem impressions of either 

 Plu/llntheca, Eqiiisetites, or ScMzoneura. The evidence of these plant remains 

 would seem to indicate a Jurassic age for the beds and a horizon equivalent to 

 that of the beds in the vicinity of Mingenew." 



Further confirmation of the presence of Jurassic rocks in the neighbour- 

 hood of Derby is afforded by the occurrence of fossil plants which have been 

 described by Antevs (1913). These include Thinnjeldia Feistmanteli from 

 Mayils Well, near Derby, occurring in a light gray clay at a depth of 300 feet, 

 and Ptilophyllum ? sp. from Point Torment, 32 miles from Derby, in a soft, 

 coarse, reddish sandstone at a depth of 30 feet. 



The examination of the specimens, described above, from Mingenew shows 

 a very remarkable lithological similarity lietween the Jurassic sandstones in 

 which the fossils occur in Western Australia and Queensland. This is a dark- 

 red, ferruginous sandstone and, if collections from the two States were mixed, 

 it would indeed be difficult to separate the Queensland from the Western Aus- 

 tralian specimens. There is also an indication of the occurrence of a similar 

 type of rock containing Ptilnphyllu.m in the Derby district in Antevs' descrip- 

 tion of fossil plants from that area, quoted above. 



Attention has previously been called to the widespread d('velo|)nient of this 

 rock in Queensland and to the probability of it indicating a well-marked horizon 

 in the Walloon Series (Walkom, 1918, p. 50). Possibly it is the result of some 

 special climatic conditions and it gives indication of the synchronous deposition 

 of the strata over a comparatively wide area. It should certainly jirove a 

 very valuable horizon when more detailed stratigraphical work is done on tlie 

 Jura-ssic strata of Australia. 



In writing on the sub.iect of Geologic Climates, F. H. Knowlton refers to 

 the subject of Red Beds (1919, p. .500) and his remarks may be quoted here 

 as having some bearing on the indications afforded by this widespread develop- 

 ment of a red sandstone in regard to the climatic conditions of the period 

 during' which it was deposited. He says: — "At this point I may stop for a 

 moment to consider the deductions to be drawn from the presence of red beds. 

 Most geologists interpret the presence of red beds as an indication of aridity. 



