262 
Mr. Etheridge, of Sydney, to whom the specimen was sub- 
mitted, referred to the Archeocyathine. There can be little 
doubt that the specimen came from one of the local rocks, as 
it carries a close lithological resemblance to them. This adds 
a palæontological proof that these beds belong to the purple 
slates division; to which, on the grounds of their strati- 
graphical position and lithological features, they had already 
been referred. As the purple slates division cccupies the 
superior position in the Mount Lofty series, it fixes the latest 
time limits that can be applied to those members of the series 
which are inferior to these beds. 
(B) Brighton Limestones and Siliceo-calcareous 
Series. 
Between the Tapley's Hill shales and the purple slates 
there is a belt of calcareous rocks which, from earthy and 
siliceous limestones, in their lower beds, pass up into strong 
and good limestones near their upper limits. The typical 
order of their occurrence is as follows: — 
Approximate 
thickness. 
(a) Buff-coloured (dolomitic) limestone ү 8 feet 
(b) Pink-coloured (oolitic) limestone ... ... 15-20 feet 
(c) Blue-coloured (siliceous) limestone ... 15-20 feet 
(d) Dark-coloured (very siliceous) limestone 400 feet 
(а) The top bed of this division is a yellowish or bufi- 
coloured dolomitie limestone, averaging about eight feet in 
thickness. It is a very persistent member of the series, and 
is found in precisely the same relative position, in these. 
beds, both to the south of Brighton and in the Flinders 
Ranges. It has not been applied locally to any economic 
purpose. Its toughness under the hammer makes it unsuit- 
able for stone-breaking. Nodules and incrustations of mag- 
nesite are often found in its vicinity. 
(b) Underlying the dolomitic limestone is a thick, strong 
limestone, of a brownish-pink colour, commonly known as 
“the pink limestone." Іп structure it is finely oolitic, and is 
the purest limestone of this calcareous group, averaging 86 
per cent. of caleium carbonate. It has an extensive use for 
road metal, along the line of its outcrop, and is one of the 
chief constituents used by the South Australian Portland 
Cement Company, at Brighton, for manufacturing an hy- 
draulic cement of excellent quality. 
(c) The blue (siliceous) limestone immediately underlies 
the pink-coloured limestone. The line of distinction is not 
