308 E. J. STATHAM. 
deposits are frequently some considerable distance back from the 
creek with intervening marginsof swamp. The same phenomenon 
is observable on the Brunswick River, notably on the south branch 
in which no oysters exist, whilst large banks of shell are to be 
found. One of these deposits at a spot known as Tyagara-Grass, 
has been extensively worked for road material, and the shell is 
apparently of the same age and in the same variety as to be found 
in the heaps previously mentioned as occurring on the Richmond 
River. It is however remarkable that this locality is a long way 
back from the stream, and cut off from it and from the high-land 
by intervening belts of swamp and brush, yet, along with the shell 
are numerous blocks and boulders of basalt as well as stone chips 
and water-worn pebbles. 
The antiquity of this deposit is unquestionable, and it affords 
evidence that estuarine conditions similar to those observable at 
the North Creek of the Richmond River at one time existed. 
That the deposits are more ancient than those at North Creek 
does not necessarily follow, as I shall show that causes of change 
have been in operation which have brought about a more rapid 
. alteration in this instance. The range of tide is considerably 
greater in the Brunswick than it is either in the Tweed to the 
North, or the Richmond to the South, due, I conceive, to the 
obstruction of the tidal current by the projection of Cape Byron, 
consequently the silting up of the Brunswick River with sand 
brought in by the flood tide, has been more rapid and thorough ; 
this section moreover being aided by the insignificance of any 
flushing action due to land-floods, the watershed of the Brunswick 
being very limited. The South Arm has almost entirely silted up, 
and loses itself in a succession of flats and swamps. 
On the larger rivers, particularly the Clarence and Richmond, 
the silting up by the in-draft of sea-sand has taken place to a 
very great extent, as evinced by the shoaling of the Woolowaya 
Estuary and the Broadwater on the Clarence, and the Richmond 
River Broadwater, which apparently are each filled in the same 
way by tidal action rather than by flood deposit, or the contribu- 
