189 
Examples of this sponge have been found in the rocks of 
the Northern Hemisphere as low down as the Ordovician, but 
so far as I know they have not hitherto been detected in 
beds of Cambrian age. It was therefore with some interest 
that I discovered their presence in two transparent sections 
made of the Curramulka limestone. Hyalostelia has regular six- 
rayed spicules, often with one ray much longer than the rest, and 
these are interlaced with elongated spicular rods. All these 
features are apparent in the Curramulka specimens. In the 
stone the spicules and rods are not in their natural position, but 
are scattered irregularly in the matrix. The long-rayed arm was 
clearly seen in one of the spicules, but as its position was not 
coincident with the plane of the section, it was ground away be- 
fore the required thinness was obtained. The same thing 
occurred with the rod-shaped spicules which have been cut at 
various angles in the transparent sections. The remains of this 
sponge obtained so far are very limited, and not under the most 
favourable conditions; it would therefore be premature to 
attempt a specific determination of the Curramulka specimens, 
but their very small size renders it probable that they are specific- 
ally distinct from the examples of Hyalostelia already known. 
EXPLANATIONS TO PLATE II. 
Fig. 
l-la. Hyolithes conularioides. Lateral view and demi-sectional out- 
line. Enlarged 2x. 
2. Hyolithés communis. Nat. size. 
3-3). Salterella planoconvexa. Dorsal and ventral aspects, and _ sec- 
tional outline. Nat. size. 
4, Stenotheca rugosa. Lateral view. Enlarged 3x. 
5. Orthis peculiaris. Nat. size. 
6-6a. Orthisina compta. Dorsal (?) valve and cardinal area of the same. 
Enlarged 2x. 
7a-7c. Platyceras Etheridgei. Three views, enlarged 2:5x. 
8a-8b. Ophileta subangulata. Upper surface and lateral aspect, enlarged 
about 3x. 
9. Free cheek of unknown trilobite. Enlarged 1-dx. 
10. Ambonychia macroptera ; much enlarged. 
1]. Olenellus (7) Pritchardi. Enlarged 2x. 
12. Microdiscus subsagittatus. Enlarged 3x. 
13. Another free cheek. Enlarged 2x. 
