152 
Geology of Sydney. 
saurs, having enormous cavities in their craniums for 
the lodgment of the eyes. This type of reptiles is 
lestricted to this single age of the world. Here also 
crawled reptiles resembling gigantic lizards, semi- 
aquatic or purely terrestrial in their habits, having 
feet for walking, instead of flat oar-like extremities for 
swimming.” 
“ These forms all disappeared with the dawn of a 
new era. Their bones lie buried in the geological 
cemeteries of Europe. It is almost incredible that 
information so exact can be drawn from the few 
scattered fragments which have been brought to light; 
but such is the unity and persistence of plan which 
runs through the different classes of the animal king- 
dom, that a single tooth, whether of a living or an 
extinct species, will often suffice to enable the expert to 
disclose all the zoological relationships of the animal 
to which it belonged, to delineate its form, and size, and 
habits of life ; as the architect from a single capital 
rescued from a ruined edifice can declare not only the 
general style of the entire architecture, but can repro- 
duce the size and proportions of the temple whose spirit 
and method it embodies. Not less sublime than the 
work of the astronomer, who sits in his own observa- 
tory, and, by the use of a few figures, determines the 
existence and position in space of some far-off, unknown 
orb, is that of the palaeontologist, the astronomer of 
time-worlds, who, from the tooth of a reptile, or 
the bony scale of a fish found thirty feet deep in the 
