92 
Geology and Physical Geography : 
the following species have been also found in the drifts of appa- 
rently Miocene age at Tanjil : — Spondylostrobus Smythii , Phy- 
matocaryon Mackayi , Celyphina McCoyi , Conchotheca turgid a, 
and Platycoila Sullivani. Another species, Plcsiocapparis 
prisca , has been obtained in auriferous gravels of Miocene age 
beneath Older Volcanic layers at Hoddle’s Creek, Upper Yarra. 
Older Volcanic Rocks. 
The different Volcanic rocks of the Tertiary period are so 
associated with the sedimentary layers that, in order to convey a 
clear idea of their relations, it is advisablo to describe them in 
their order of sequence with the latter, instead of in a special 
chapter by themselves. 
The Older Volcanic rocks are the latest products, and mark dis- 
tinctly the close, of the Middle Tertiary or Miocene era. There 
do occur, occasionally, thin volcanic layers, in terstratified with the 
Miocene sedimentary beds, showing that vulcanicity was not 
altogether dormant during the formation of the latter, but the 
greatest volcanic activity evidently took place at the close of the 
period. Where undecoinposed, the Older Volcanic basalts are 
usually dark, deuse, and solid, of a polygonally jointed and some- 
times distinctly columnar structure, and composed chiefly of 
augite, labradorite, olivine, and specular iron. They are, however 
as a rule, either wholly or partly decomposed. In the former 
condition, they consist of red, yellow, purple, brown, and nearly 
white amygdaloidal clays, containing hard lumps of less de- 
composed rock showing concentric structure ; in the partly de- 
composed state the rock exhibits in sections the appearance of a 
conglomerate of such concentric masses in a clay matrix. 
In every locality throughout the colony where the Older Volcanic 
rocks are at the surface the soil immediately resting on or derived 
from them is of great fertility and of exceptional value for agri- 
culture. In the Neerim, Brandy Creek, and other districts in 
Gippslaud, the natural vegetation growing on such soil is of a 
most luxuriant sub-tropical character, forming a serious impedi- 
ment to the labours of the selectors, who, during late years, have 
eagerly taken up every available acre of such land. 
The sources whence the Older Volcanic lava streams issued have 
not yet been distinctly recognised ; no well-marked points of erup- 
tion such as are common in the Newer Volcanic districts have been 
observed, and it would appear that the original volcanic cones 
have been entirely removed by subsequent denudation, so that it 
would only be in what are now narrow or small pipe-shaped dykes, 
easily passed over unobserved, and probably far distant from where 
the Older Volcanic rocks remain in considerable area, that we 
might look for the vents whence the flows were poured forth. The 
original exteut covered by Older Volcanic rocks was once very 
