RELATIONSHIPS OF THE AUSTRALIAN CAINOZOIC SYSTEM. 
The Evidence of the Complex-structured Foraminifera in the 
Australian Tertiary System. 
The shells of foraminifera exhibit great diversity of form, as 
well as a wide range of complexity in shell-structure. It is too 
often assumed that, because these ubiquitous marine organisms 
belong to the lowest phylum of the animal kingdom, they cannot 
therefore be of value in helping to decide the age of the beds in which 
they occur. This, however, is far from the truth, for, prima facie, 
no one with a special knowledge of palaeontology would dispute the 
proofs of the restriction of the Nummulites to a limited series of 
strata (Eocene and Oligocene), or ignore the zonal value of certain 
species of the genera Lepidocyclina and Miogypsina. 
With regard to the genera of foraminifera which possess simply 
constructed tests, we may for the present dismiss these from 
consideration ; for, although they have a certain distributional 
value in affording evidence of geographical facies dominated by local 
conditions of life, or controlled by sedimentation and hydrographical 
factors, there is a much more important section to be dealt with in 
the specialized forms constituting the Family Orbitoididae, and 
some other more or less related forms with highly specialized shell- 
structure. 
Gypsina howchini, Chapman. — I have already shown* how closely 
the above species agrees with the Miocene ancestor of Gypsina, viz., 
Miogypsina. The chief difference lies in the absence of the vertical 
pillars as seen in cross-sections of Miogypsina ; the only differentia- 
tion of the chamberlets in the median plane in the test of G. howchini 
being in their more spacious character.]" 
Amphistegina lessonii, d’Orbigny.— The inequilateral Amphis- 
tegina took the place of the equilateral Nummulites towards the close 
of the Oligocene, and was the predominant form in many foraminiferal 
deposits of Miocene age. 'I 
Cycloclypeus pustulosus, Chapman. — This species is, so far as 
known elsewhere, confined to the Miocene (Burdigalian), being 
found in the Island of Santo, New Hebrides, where it is associated 
with Miogypsina hurdigalensis, Giimbel sp. ; M. complanata , 
Schlumberger ; M. irregularis, Michelotti sp. ; Amphistegina lessonii, 
d’Orbigny ; Hcterostegina depressa, d Orb. ; H. margaritata , Schl. , 
Lepidocyclina maitini, Schl. ; L. andrewsiana, Jones and Chapman ; 
and L. insulae-natalis, J. and C. 
With regard to the Orbitoididae, this group has a range frorn the 
Cretaceous to the Miocene. In southern Australia these foraminifera, 
represented by the Oligocene-Miocene genus Lepidocyclina, play the 
very important part of forming a large proportion of certain lime- 
stones such as those of Batesford and Keilor ; whilst they are also 
* I Toe. Roy. Soc. Viet., vol. xxii. (N.S.), pt. 2, 1910, p. 291. 
t Proc. Roy. Soc. Viet., tom. supra cil., pi. liii., fig- 5. 
t Soc also loc. supra cit., p. 308. 
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