RELATIONSHIPS OP THE AUSTRALIAN CAINOZOIC SYSTEM. 
to say that neither Brady nor von Hantken made sections of the 
specimens, and the very large size of the Amphistegina was no doubt 
a misleading factor in the determination/’ 
This common little nummulinoid species of the Australian 
Tertiaries is without doubt referable to A. lessonii, d’Orbigny ; and 
the fresh or unworn examples resemble the variety found in the 
Vienna Basin, known as A. hauerina, d’Orb. Some of the larger 
specimens occurring in the Balcombian marls of Muddy Creek, 
T. Woods remarked upon as being “ glazed with a ferruginous 
deposit.” It appears, however, that abrasion and polishing has 
occurred in these examples, presumably by aeolian agency, and that 
they have been subsequently stained by the action of ferruginous 
water. The large sized tests of the Amphisteginae found in the Muddy 
Creek shell-marl can be matched by those from moderately shallow 
water of tropical or subtropical areas. At Funafuti the examples 
of this genus are similarly of large size, and frequently wind-worn 
or even polished ; the latter character appearing on specimens of 
the tests from various depths in the deep boring. Amphistegina 
lessonii occurs at Funafuti at all depths down to 200 fathoms, and it 
was at its largest at about 36 fathoms.* 
hor the convenience of workers in other fossil groups who may 
not be conversant with the characters separating the genera 
Amphistegina and Nummulites , the following table is given. 
Common and differential characters of — 
Amphistegina. 
Arrangement of 
chambers 
Spiral, equitant 
Peripheral aspect . . 
Asymmetrical. Chambers 
more spacious on the lower 
side 
Umbilical axis 
With unequal-sized cones of 
finely tubulate shell sub- 
stance ; apices of cones 
directed i nward 
Septa 
Curved backward, angu- 
lately ; and either with 
simple septal wall, or with 
ill-developed interseptal 
canals 
Alar prolongations, 
Forming supplementary lobes 
or lateral develop- 
on each side ; those of the 
ment of chambers 
lower surface nearly 
severed, excepting for a 
narrow neck, and forming 
the astral lobes 
Aperture 
A rotaline or crescentic slit 
on the lower face 
Nummulites. 
Spiral, equitant 
Symmetrical ; therefore 
chambers equal on both 
sides 
Without umbilical cones 
Roundly arched, not thrown 
so far backward. Inter- 
mediate skeleton and 
intersepta] canal-system 
highly developed, resulting 
in double shell-walls. 
Alar prolongations com- 
pletely covering the earlier 
convolutions, and en- 
closing cither a simple 
laminar space, or one sub- 
divided into loculi 
A simple V-shaped slit at the 
junction of the penultimate 
whorl 
* Linn. Soc. Journ. Zool., vol. xxviii., 1902, p. 414. 
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