at the Don and Tamar Rivers. 101 
estuary of the Tamar known as the “‘ Middle Arm” trends to 
the southward and westward, and the strata along its banks’ 
have a general, inconsiderable, and nearly uniform dip 
‘toward the east; therein agreeing with the disposition of 
the beds in the ‘‘ West Arm.” 
The rocks which present, first, are white sandstone, 
succeeded by arenaceous brown shale and clayey con- 
glomerate, with which occur silicified stumps and roots 
of trees: grits, clayey conglomerates, and slaty argillaceous 
beds, all more or less fossiliferous, follow. The channel is 
- very devious and very shoal, with extensive mud-flats on 
one hand or the other, or on both: on the south shore the 
land is low and nearly level, with a line of greenstone- 
capped hills between it and the main course of the Tamar. 
The mud-flats prevented the exact survey which ought 
to have been made of this portion of the bay. At the 
extremity of the “Middle Arm” a rivulet enters the 
bay, and on the eastern side of the junction is the 
site of the lime-quarries formerly worked by Govern- 
ment: they consist of arenaceous conglomerate, argilla- 
ceous slaty beds, and massive beds of limestone, the first 
and last of which abound with fossil shells; amongst 
them Bellerophon, Micromphalus, Pachydomi, Pectenides, 
Platyschisma rotundatum, and another species—Productu 
and Spirifer Stokesti and Tasmaniensis, &c.; together 
with several species of Fenestelle, of Stenopore, &e. &c. 
The colour of this limestone varies from brownish yellow, 
through ashy gray, to slate blue: the dip of the beds is to 
the eastward. 
About a mile distant, in a north and westerly direction, a 
limestone is quarried, burnt, and prepared for the market by 
Mr. De Little, which differs in many particulars from that 
already described. It is nearly homogeneous in substance, 
H3 
