SEDIMENTARY ROCKS OF THE LOWER SHOALHAVEN RIVER. 333 
whole are very barren of fossils. In one or two horizons, 
however, internal casts consisting entirely of brachiopods 
were fairly common. At the Grotto near Nowra, good 
internal casts of Spirifer are common, and on the range 
between Burrier and Longreach, sandstone made up of 
masses of Productus was found. 
River Gravels and Alluvium.—These are comparatively 
of recent age, and are found on the inside bends of the 
river as far as it was explored. ‘The river gravels consist 
of a great variety of rocks and get coarser the higher we 
ascend. Gold occurs in cracks almost anywhere in the 
river bed, but only in small quantities. 
Habitats of the Paleozoic Fauna.—This is a very fasci- 
nating but difficult subject, and one hardly as yet touched 
upon. The clearness of local conditions under which the 
Wandrawandian Series were formed may however throw 
some light on the subject. Inthe storm tossed waters near 
the old shore, only very strong shelled molluscs could sur- 
vive. Here we find Edmondia and Mceonia flourishing. The 
Grassy Gully beds contain brachiopods, with a few pelecy- 
pods ofa peculiar littoral nature, such as Aphanaia; these 
shells probably lived under the lea of the neighbouring 
island, and evidently preferred quiet water with a sandy 
bottom. They are very similar in appearance to the com- 
mon mussels (Mytilus) and probably had the same habitat. 
Here too, occasional pteropods drifted in from the open 
ocean and their delicate shells had a chance to be preserved. 
In the Wandrawandian period we see a shallow sea with 
a muddy bottom in which countless pelecypods such as 
Pachydomus, Meeonia, Pleurophorus, Choenomya, Meris- 
moptera abounded. The gasteropods Mourlonia and 
Platyschisma, together with the Spirifers seem to have 
been ubiquitous and to have lived anywhere. Goniatites 
probably was like the pteropods and floated on the open 
