102 
Geology oe Sydney. 
Some very remarkable fish teeth were found in 
Triassic rocks near Bristol, to which Agassiz gave the 
name Curatodus. The teeth were the only portions of 
the creature known. Strange to say, long afterwards 
a fish was discovered living in Queensland rivers with 
similar teeth. It is known as Ceratodus or mud-fish. 
This unexpected discovery of the living animal 
throws much light on its distinguished English 
ancestor of Triassic times. The survival in Australia 
of this remnant of ancient life is full of interest to the 
geologist. But it is not the only instance of the kind 
known. A survival of forms, allied to creatures that 
lived in Secondary times, is not at all uncommon 
here. Indeed, Australia has been called (in a 
geological sense) the land of living fossils. 
The Port Jackson shark (Cestracion) is an equally 
remarkable living fossil. It is the sole survival of a 
group of sharks remarkable for the pavement of 
crushing teeth which line the mouth. Sharks of this 
type were extremely common in the European seas of 
the Secondary period. Buckland first drew attention 
to the fact that in far-off geological times these 
sharks lived side by side with the Trigonias, and it is 
a fact of surpassing interest to see “ the same comrade- 
ship kept up on the distant coast of Australia.” 
It may not be generally known that the beautiful 
Trigonia shell of our harbour is a genus originally 
known as extinct. The first descriptions were pub- 
lished from fossil forms. It was a welcome discovery 
