246 
additions to the cambrian fauna of 
South Australia. 
By R. Etheridge, junk., Hon. Fellow, Curator of the 
Australian Museum, Sydney. 
[Read April 4, 1905.] 
Plate XXV. 
Our Cambrian Fauna is, comparatively speaking, of so 
limited a nature at present that additions are always most 
welcome. Mr. W. Howchin recently forwarded to me a 
small collection of fossils from a new horizon, aiscovered by 
himself. Mr. Howchin describes the deposit as a "shelly 
band in an oolitic limestone of much inferior thickness to that 
carrying the great reef of Archaeocyathinse, situated in the 
Flinders Range, not far from Wirrialpa." 
The limestone is, generally speaking, flesh-coloured, and 
the fossils break out on fracture in fairly good condition. The 
oolite grains t^ppear under two conditions : either on a frac- 
tured surface, as small spherical or oval bodies up to one 
millimetre in diameter ; or, on weathered faces, in natural 
section, when their structure, under an ordinary pocket lens, 
is very misleading. In this condition they present the appear- 
ance of minute corallites of a fasciculate Rugose coral, with 
definite septa, and are closely packed on some pieces of lime- 
stone, or sparsely distributed on others. On placing a thin 
slice of this pseudo-coral, prepared for the microscope, under 
a high-power objective, the supposed corallites at once resolve 
themselves into oolitic grains of a peculiar structure. These 
grains are wholly composed of concentric layers, or zones, of 
carbonate of lime, with or without a central nucleus of clear 
calcite, accompanied by a radial structure, and it is the latter 
that simulates the appearance of a septate coral. In fact, 
these grains when seen in natural or w^eathered transverse sec- 
tion resemble very minute Archseocyathinse, especially when 
the pellicle is thin, or of small diameter, and enclosing a clear 
nucleus. This radial structure is not uncommon in oolitic 
grains, but its remarkable resemblance to a minute coral has 
not before come under my notice. Between crossed Nicols the 
black cross is clearly seen in places, indicating crystalline and 
not organic structure. No organic nucleus was observed in 
any case. 
I have succeeded in determining one Trilobite, Ave 
Brachiopods, and one Pteropod, but these, with the excep- 
tion of the Pteropod, bear no specific relation to the more 
copious fauna, described by the late Professor R. Tate,*^ 
* Tate— Tr.R.S.S.A., 1892, xv.7parr27r7m 
