RELATIONSHIPS OF THE AUSTRALIAN CAINOZOIC SYSTEM. 
desori, O. retroflera, O. eocaena, O. minuta, Carcharodon auriculatus, 
and OC. megalodon. Of these, 2 are northern Cretaceous forms, 11 
are Hocene, 1 Oligocene,* 11 Miocene, and 6 Pliocene. <A closer 
scrutiny of these species reveals the fact that, whereas the genus 
may be recorded from both Eocene and Mioctne, yet in regard to 
abundance and ubiquity the evidence of the species, as before stated, 
is decidedly in favour of a Miocene age for the majority of the 
fish remains in the older portion of our Tertiaries. 
With reference to the other fish remains in the Austra- 
lasian Tertiary, it is interesting to note that the Chimaeroids have a 
more ancient history elsewhere, whilst around Australia they lived 
in large numbers in the Balcombian and Janjukian seas. Our 
Tertiary Labrodon is comparable with the typical Miocene species 
of South Carolina, the Vienna Basin, Italy, Sicily, and Brittany. 
The Australian gymnodont, Diodon formosus, is most nearly allied 
to D. vetus from the Miocene phosphate beds of South Carolina. 
The fossils of this genus are commonest as Miocene forms. 
Mollusca.—Of the tetrabranchiate cephalopods, the <Aturia 
australis of McCoy is a typical fossil in the Australasian Tertiaries. 
It had an extraordinarily long existence, being found in the 
Balcombian, the Janjukian, and the Kalimnan series ; although 
it seems to be more common in the blue clays of the Mornington 
and Muddy Creek beds (Balcombian), where it often attains a 
large size. An exceptionally fine specimen from Muddy Creek in 
the National Museum collection measures 17.5 cm. (nearly 7 
inches) in diameter, and about 6 cm. across in the umbilical region. 
This species is distinct from the Lower Eocene form, A. ziczac, to 
which it was formerly referred, in having more compressed sides. 
In this respect it is similar to A. aturi, Basterot, originally described 
from the Miocene of Dax, France, and also occurring at Turin and 
Malta in beds of the same age. 
The true Nautili are also well represented in our faunas, but up 
to the present only one form has been described, viz., N. geelong- 
ensis, Foord,} which that author compares with N. regalis, J. Sow. 
The London clay species differs, as Foord remarks, in that “it is 
a more inflated shell, and its sutures much less flexuous.” Examples 
of what appear to be the same form, in the National Museum collec- 
tion, are from the Moorabool Valley, Victoria, and the clifis of the 
Lower Murray River in South Australia (Janjukian). 
The dibranchiate cephalopod, Spirulirostra, is one of the most 
remarkable genera of the Australian fauna. The only southern 
species, S. curta, made its appearance suddenly, but after a very 
short existence as quickly died out. It is strictly confined to 
* The low number of records from the Oligocene is probably accounted for by the fact that 
certain beds of this system were previously regarded as Eocene. A revision of these records 
would possibly raise the number for the Oligocene. 
+ Cat. Foss. Cephal. Brit. Mus., pt. 2, 1891, pp. 332, 333, figs. 69a—c. 
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