134 
On some Fossil Plants 
There are multitudinous and imperfect, but indubitable casts 
and traces of the steins, roots, &c., of Cyperacece and Restiacese, 
intermixed with twigs and roots of ligneous plants. Two shells 
are figured by Strzelecki as common to this and the limestone 
of Risdon, on the opposite side of the Derwent, and the two 
calcareous beds are considered to be identical—a fact which I 
question; for to my apprehension these limestones differ in appear¬ 
ance, structure, solidity, and contents. That from Risdon quarries 
is compact, moderately hard, of a granular and somewhat earthy 
structure, homogeneous composition, and even colour of yellowish 
brown, with two or three fresh water shells distributed throughout, 
and some casts of ligneous matter; characters which sufficiently 
distinguish it if compared with the description I have given of 
that from near Elizabeth-street, Hobart Town. The Risdon lime¬ 
stone seems to have been deposited from a tranquil lake, fed by 
calcareous and other springs, and without tributary streams of 
sufficient magnitude or force to introduce great variety in the 
shape of vegetable matter, or essentially to influence the nature 
of the sedimentary substance. 
The Elizabeth-street limestone appears to have been formed in 
a shallow sedgy valley, maintained chiefly by calcareous springs, 
but occasionally dry, or nearly so, and subject to temporary inun¬ 
dations from higher ground, or from the quiet sinuous arm or 
basin of some neighbouring river. 
The same calcareous source may thus in turn have supplied 
material for both these local deposits ; and afterwards have 
furnished that which is scattered amongst the greenstone boul¬ 
ders ; and even now may be furnishing forth somewhere in the 
estuary of the Derwent a fresh place for future observation and 
conjecture. 
Second. The shale and sandstone yielding the fossil remains 
next to be noticed are also from the vicinity of Hobart Town, 
and lie at no great distance from the limestone just mentioned, 
though in geological relation widely separated, the former be¬ 
longing to the coal strata, the latter to the most recent of the 
tertiary beds. 
The shale is from the summit of “ Swan’s” Hill, where the 
Launceston road crosses its ridge. 
