A LARGE SPIRAL STRUCTURE FROM WESTERN QUEENSLAND. 
205 
The grooving is at an angle, of 7° to the general length of the specimen. 
On Plate XXXII, fig. 16 the line of junction of the two surfaces may be seen 
starting from the base of the main break in the specimen and running upwards 
and to the right from that point. In this orientation the upper portion as 
shown on Plate XXXII, fig 16 was the embedded side. 
The Cretaceous beds of Western Queensland outcrop over vast areas 
of plains and dip at. only very gentle angles. This angle of 7° on the specimen 
suggests that it was contained in the rocks lying along, or else at a very 
slight angle to the bedding plane. 
Associated Structures . — Accompanying the specimen were masses of 
closely packed, flattened, nodule-like structures that Mr. Ellis in his letter 
appropriately compared to "a batch of buns.” These are composed of similar 
brown, calcareous sandstone of the fontainebleau type. As has been mentioned 
the whorls at one end of the spiral abut upon a mass of such objects ; but, 
unfortunately, owing to the specimen being there incomplete, the relationship 
of the spiral to the associated nodules is not to be determined. 
Age . — -Duthie Park is near the margin of the Great Artesian Basin in a 
region where the lowest beds (Roma Series) are overlapped by those of the 
Tambo Series. In this great basin of Cretaceous deposits the lower beds are 
of marine origin and are divisible into two series, the lower of Roma Series 
being of Aptian age and the upper or Tambo Series belonging to the Upper 
Albian ( see Whitehouse 1928). Above the Tambo Series lies the Winton Series 
of non-marine beds and which, from available evidence, has a maximum 
thickness of at least 4,000 feet. The gradation from the Tambo Series to the 
Winton Series is complete. The lithology of the two Series is identical, the 
typical rock types being blue clays with bands of concretionary, calcareous 
sandstones. It is never possible in the field to place a line dividing the two 
Series ; for the Tambo Series, so richly fossiliferous in its lower phase is, in 
its upper beds, almost entirely barren of fossils. Prolonged search in such 
upper beds of the Tambo Series may bring to light some fragments of 
Inoceramus or an Aucellina. With identical lithology in the two Series and a 
progressive decrease in the abundance of fossils in the lower it is usually impossible 
to say, in any pertinent area, where the marine Tambo Series ends and where begins 
the Winton Series, which has yielded plant remains from a few localities but never 
marine fossils. The work of Mr. C. Ogilvie and myself shows that, as a field 
guide, there are only two criteria that at present serve to distinguish definitely 
Tambo from definitely Winton Series beds. The typical concretions of the 
Tambo series are flattened, oval things (" Damper shaped ”), while those of the 
Winton Series are usually spherical (" Cannon-Ball types ”). Also, yellow- 
shale pellets are common in the sandstones of the Winton Series but rare in 
such beds from the Tambo Series. 
There are no fossils in the matrix of these specimens ; but from their 
geographical position in the basin it would seem that the beds of Duthie Park 
D 
