ON THE TERTIARY DEPOSITS OF AUSTRALIA. 71 
which have a wide distribution, we see a great difference between 
red T 
specimens gathered in different provinces ake for instance 
Mytilus latus, k., or the common Australian mussel, which is 
one of the few ett ie alarge a New ealant 
time. But from those or other instances that might be alleged, 
we find pretty certainly manifest at the present day local differ- 
ences of form, character, &c., in otherwise identical species. 
eed it seems to me that there is not the same variety in our 
rtiary beds, and that this greater or less variability in remote 
dietricte might be made to form a valuable guide to the chronology 
of the te One hin sidlon seit is certain, which is that 
ary 
rather that of the aminarian zone. 2nd. That colour, “which. is 
an important element in ae variety in existing shells, is 
absent from the fossils. 3rd. The tertiary area at our disposal 
for investigation, though wide, is not nearly so extensive as the 
area of the provinces scare ar by me. Still, making all those 
have in our ormations a much ter uniformity i 
marine life, pecies more constant in character, than what is 
witnessed in — Fag Australian seas. may seem of 
This fact 
small importan timating our chronology, but I venture to 
submit that it i isa the which will lead in the end to valuable 
data ether we could ever hope by its aid to erect sub-di- 
visions in our tertiary formations may appear doubtful, yet it 
must be of importance until: the percentage system can be 
applied. 
t mere external resemblance. Som he f cl 
in character the fossils known in the English by 
what the learned p is te “mimetism.” The m- 
blance is so close that some might even suppose the identity of the 
fossils. This is especially seen in Voluta antiscalaris, M‘Coy, and 
