FOSSIL FORAMINIFERA AND RADIOLARIA.
=Protozoans, Their Structure.--=
The animals forming the sub-kingdom PROTOZOA ("lowliest animals"), are
unicellular (one-celled), as distinguished from all the succeeding higher
groups, which are known as the METAZOA ("animals beyond"). The former
group, Protozoa, have all their functions performed by means of a simple
cell, any additions to the cell-unit merely forming a repetitional
or aggregated cell-structure. A familiar example of such occurs in
pond-life, in the Amoeba, a form which is not found fossilised on account
of the absence of any hard parts or covering capable of preservation.
Foraminifera and Radiolaria, however, have such hard parts, and are
frequently found fossilised.
=Foraminifera: Their Habitats.--=
The _FORAMINIFERA_ are a group which, although essentially one-celled,
have the protoplasmic body often numerously segmented. The shell or test
formed upon, and enclosing the jelly-like sarcode, may consist either
of carbonate of lime, cemented sand-grains, or a sub-calcareous or
chitinous (horny) covering. The Foraminifera, with very few exceptions,
as _Mikrogromia_, _Lieberkuehnia_, and some forms of _Gromia_, are all
marine in habit. Some genera, however, as _Miliolina_, _Rotalia_ and
_Nonionina_, affect brackish water conditions.
Since Foraminifera are of so lowly a grade in the animal kingdom, we may
naturally expect to find their remains in the oldest known rocks that show
any evidence of life. They are, indeed, first seen in rocks of Cambrian
age, although they have not yet been detected there in Australian strata.
=Cambrian Foraminifera.--=
In parts of Siberia and in the Baltic Provinces, both Cambrian and
Ordovician rocks contain numerous glauconite casts of Foraminifera,
generally of the _Globigerina_ type of shell. In England some Middle
Cambrian rocks of Shropshire are filled with tiny exquisitely preserved
spiral shells belonging to the genus _Spirillina_, in which all the
characters of the test are seen as clearly as in the specimens picked out
of shore-sand at the present day.
=Silurian Foraminifera.--=
The Silurian rocks in all countries are very poor in foraminiferal shells,
only occasional examples being found. In rocks of this age at Lilydale,
Victoria, the genus _Ammodiscus_, with fine sandy, coiled tests, is found
in the Cave Hill Limestone.
So far as known, hardly any forms of this group occur in Devonian strata,
although some ill-defined shells have been found in the Eifel, Germany.
=Carboniferous Foraminifera.--=
The Carboniferous rocks in many parts of the world yield an abundant
foraminiferal fauna. Such, for instance, are the _Saccammina_ and
_Endothyra_ Limestones of the North of England and the North of Ireland.
The Australian rocks of this age have not afforded any examples of the
group, since they are mainly of estuarine or freshwater origin.
[Illustration: =Fig. 63.--PALAEOZOIC and MESOZOIC FORAMINIFERA.=
A--Nubecularia stephensi, Howchin. Carbopermian. N.S.W.
B--Frondicularia woodwardi, Howchin. Carbopermian. N.S.W.
C--Geinitzina triangularis, Chapman and Howchin. Carbopermian. N.S.W.
D--Valvulina plicata, Brady. Carbopermian. West Australia.
E--Vaginulina intumescens, Reuss. Jurassic. West Australia.
F--Flabellina dilatata, Wisniowski. Jurassic. West Australia.
G--Marginulina solida, Terquem. Jurassic. West Australia.
H--Frondicularia gaultina, Reuss. Cretaceous. West Australia.
]
=Carbopermian Foraminifera.--=
In Australia, as at Pokolbin, New South Wales, in the Mersey River
district, Tasmania, and in the Irwin River district, Western Australia,
the Permian rocks, or "Permo-carboniferous" as they are generally called,
often contain beds of impure limestone crowded with the chalky white
tests of _Nubecularia_: other interesting genera occur at the first named
locality as _Pelosina_, _Hyperammina_, _Haplophragmium_, _Placopsilina_,
_Lituola_, _Thurammina_, _Ammodiscus_, _Stacheia_, _Monogenerina_,
_Valvulina_, _Bulimina_, (?)_Pleurostomella_, _Lagena_, _Nodosaria_,
_Frondicularia_, _Geinitzina_, _Lunucammina_, _Marginulina_, _Vaginulina_,
_Anomalina_ and _Truncatulina_. The sandy matrix of certain _Glossopteris_
leaf-beds in the Collie Coal measures in W. Australia have yielded
some dwarfed examples belonging to the genera _Bulimina_, _Endothyra_,
_Valvulina_, _Truncatulina_ and _Pulvinulina_; whilst in the Irwin River
district similar beds contain _Nodosaria_ and _Frondicularia_ (Fig. 63).
=Triassic Foraminifera.--=
The Triassic and Rhaetic clays of Europe occasionally show traces of
foraminiferal shells, probably of estuarine habitat, as do the Wianamatta
beds of New South Wales, which also belong to the Triassic epoch. The
Australian representatives are placed in the genera _Nubecularia_,
_Haplophragmium_, _Endothyra_, _Discorbina_, _Truncatulina_, and
_Pulvinulina_. These shells are diminutive even for foraminifera, and
their starved condition indicates uncongenial environment.
=Jurassic Foraminifera.--=
The Jurassic limestones of Western Australia, at Geraldton, contain many
species of Foraminifera, principally belonging to the spirally coiled and
slipper-shaped _Cristellariae_. Other genera present are _Haplophragmium_,
_Textularia_, _Bulimina_, _Flabellina_, _Marginulina_, _Vaginulina_,
_Polymorphina_, _Discorbina_, and _Truncatulina_.
=Cretaceous Foraminifera.--=
In the Lower Cretaceous rocks known as the Rolling Downs Formation in
Queensland, shells of the Foraminifera are found in some abundance
at Wollumbilla. They are represented chiefly by _Cristellaria_ and
_Polymorphina_.
[Illustration: =Fig. 64.--Structure in Lepidocyclina.=
A--Vertical section through test of Lepidocyclina marginata,
Michelotti sp.: showing the equatorial chambers (eq. c) and the
lateral chambers (l.c.)
B--Section through the median disc, showing the hexagonal and ogive
chambers. × 18.
Cainozoic (Janjukian). Batesford, near Geelong, Victoria.
(_F.C. Coll._)
]
=Cainozoic Foraminifera.--=
The Cainozoic strata in all parts of the world are very rich in
Foraminifera, and the genera, and even many species are similar to those
now found living. Certain types, however, had a restricted range, and are
therefore useful as indicators of age. Such are the Nummulites and the
_Orbitoides_ of the Eocene and the Oligocene of Europe, India and the West
Indies; and the _Lepidocyclinae_ of the Miocene of Europe, India, Japan
and Australia (Fig. 64).
The genus _Lepidocyclina_ is typically represented in the Batesford beds
near Geelong, Victoria by _L. tournoueri_, a fossil of the Burdigalian
stage (Middle Miocene) in Europe, as well as by _L. marginata_. A
limestone with large, well-preserved tests of the same genus, and
belonging to a slightly lower horizon in the Miocene has lately been
discovered in Papua.
[Illustration: =Fig. 65.--CAINOZOIC FORAMINIFERA.=
A--Miliolina vulgaris, d'Orb. sp. Oligocene-Recent. Vict. and S.A.
B--Textularia gibbosa, d'Orb. Oligocene and Miocene. Vict. & S.A.
C--Nodosaria affinis, d'Orb. Oligocene. Victoria.
D--Polymorphina elegantissima. P. and J. Oligocene-Recent. Vict. and
S.A.
E--Truncatulina ungeriana, d'Orb. sp. Oligocene-Recent. Vict. & S.A.
F--Amphistegina vulgaris, d'Orb. Oligocene-L. Pliocene. Vict. & S.A.
]
Some of the commoner Foraminifera found in the Cainozoic beds of Southern
Australia are--_Miliolina vulgaris_, _Textularia gibbosa_, _Nodosaria
affinis_, _Polymorphina elegantissima_, _Truncatulina ungeriana_ and
_Amphistegina lessonii_ (Fig. 65). The first-named has a chalky or
porcellanous shell; the second a sandy test; the third and fourth glassy
or hyaline shells with excessively fine tubules; the fifth a glassy shell
with numerous surface punctations due to coarser tubules than usual in
the shell-walls; whilst the last-named has a smooth, lenticular shell,
also hyaline, and occurring in such abundance as often to constitute a
foraminiferal rock in itself.
=Pleistocene Foraminifera.--=
The estuarine deposits of Pleistocene age in southern Australia often
contain innumerable shells of _Miliolina_, _Rotalia_ and _Polystomella_.
One thin seam of sandy clay struck by the bores in the Victorian Mallee
consists almost entirely of the shells of the shallow-water and estuarine
species, _Rotalia beccarii_.
* * * * *
=Radiolaria: Their Structure.--=
The organisms belonging to the order _RADIOLARIA_ are microscopic, and
they are all of marine habitat. The body of a radiolarian consists of a
central mass of protoplasm enclosed in a membranous capsule, and contains
the nuclei, vacuoles, granules and fat globules; whilst outside is a
jelly-like portion which throws off pseudopodia or thin radiating threads.
The skeleton of Radiolaria is either chitinous or composed of clear,
glassy silica, and is often of exquisitely ornamental and regular form.
=Habitat.--=
These tiny organisms generally live in the open ocean at various depths,
and sinking to the bottom, sometimes as deep as 2,000 to 4,000 fathoms,
they form an ooze or mud.
=Subdivisions.--=
Radiolaria are divided into the four legions or orders,--Acantharia,
Spumellaria, Nasselaria and Phaeodaria: only the second and third groups
are found fossil. The Spumellarians are spherical, ellipsoidal, or
disc-shaped, and the Nasselarians conical or helmet-shaped.
=Cambrian Radiolaria.--=
Certain cherts or hard, siliceous rocks of the palaeozoic era are often
crowded with the remains of Radiolaria, giving the rock a spotted
appearance. (See _antea_, Fig. 38). Some of the genera thus found are
identical with those living at the present day, whilst others are peculiar
to those old sediments. In Australia, remains of their siliceous shells
have been found in cherts of Lower Cambrian age near Adelaide. These have
been provisionally referred to the genera _Carposphaera_ and _Cenellipsis_
(Fig. 66).
=Ordovician Radiolaria.--=
Radiolaria have been detected in the Lower Ordovician rocks of Victoria,
in beds associated with the Graptolite slates of this series. In New South
Wales Radiolarian remains are found in the cherts and slates of Upper
Ordovician age at Cooma and Mandurama.
=Silurian Radiolaria.--=
The Silurian black cherts of the Jenolan Caves in New South Wales contain
casts of Radiolaria.
=Devonian Radiolaria.--=
The Lower Devonian red jaspers of Bingera and Barraba in New South Wales
have afforded some casts of Radiolaria, resembling _Carposphaera_ and
_Cenosphaera_.
[Illustration: =Fig. 66.--FOSSIL RADIOLARIA.=
A--Aff. Carposphaera (after David and Howchin). Cambrian. Brighton,
S.A.
B--Cenosphaera affinis, Hinde. Mid. Devonian. Tamworth, N.S.W.
C--Amphibrachium truncatum, Hinde. Up. Cretaceous. Pt. Darwin.
D--Dictyomitra triangularis, Hinde. Up. Cretaceous. Pt. Darwin.
]
The large number of fifty-three species have been found in the radiolarian
rocks of Middle Devonian age at Tamworth in New South Wales (Fig. 66).
These have been referred to twenty-nine genera comprising amongst
others, _Cenosphaera_, _Xiphosphaera_, _Staurolonche_, _Heliosphaera_,
_Acanthosphaera_ and _Spongodiscus_.
=Cretaceous Radiolaria.--=
Although certain silicified rocks in the Jurassic in Europe have furnished
a large series of Radiolaria, the Australian marine limestones of this age
have not yielded any of their remains up to the present. They have been
found, however, in the Lower Cretaceous of Queensland, and in the (?)Upper
Cretaceous of Port Darwin, N. Australia. The Radiolaria from the latter
locality belong to the sub-orders Prunoidea, Discoidea and Cyrtoidea
(Fig. 66). The rock which contains these minute fossils is stated to be
eaten by the natives for medicinal purposes. As its composition is almost
pure silica, its efficacy in such cases must be more imaginary than real.
=Cainozoic Radiolaria.--=
Cainozoic rocks of Pliocene age, composed entirely of Radiolaria, occur at
Barbados in the West Indies. No Cainozoic Radiolaria, however, have been
found either in Australia or New Zealand up to the present time.
* * * * *
COMMON OR CHARACTERISTIC FOSSILS OF THE FOREGOING CHAPTER.
FORAMINIFERA.
_Nubecularia stephensi_, Howchin. Carbopermian: Tasmania and New South
Wales.
_Frondicularia woodwardi_, Howchin. Carbopermian: W. Australia and New
South Wales.
_Geinitzina triangularis_, Chapm. & Howchin. Carbopermian: New South
Wales.
_Pulvinulina insignis_, Chapman. Trias (Wianamatta Series): New South
Wales.
_Marginulina solida_, Terquem. Jurassic: W. Australia.
_Flabellina dilatata_, Wisniowski. Jurassic: W. Australia.
_Vaginulina striata_, d'Orbigny. Lower Cretaceous: Queensland.
_Truncatulina lobatula_, W. and J. sp. Lower Cretaceous: Queensland.
_Miliolina vulgaris_, d'Orb. sp. Cainozoic: Victoria and S. Australia.
_Textularia gibbosa_, d'Orb. Cainozoic: Victoria and S. Australia.
_Nodosaria affinis_, d'Orb. Cainozoic: Victoria and S. Australia.
_Polymorphina elegantissima_, Parker and Jones. Cainozoic: Victoria,
Tasmania, and S. Australia.
_Truncatulina ungeriana_, d'Orb. sp. Cainozoic: Victoria, King Island,
and S. Australia.
_Amphistegina lessonii_, d'Orb. Cainozoic: Victoria and S. Australia.
_Lepidocyclina martini_, Schlumberger. Cainozoic (Balcombian and
Janjukian): Victoria.
_L. tournoueri_, Lemoine and Douvillé. Cainozoic (Junjukian):
Victoria.
_Cycloclypeus pustulosus_, Chapman. Cainozoic (Janjukian): Victoria.
_Fabularia howchini_, Schlumberger. Cainozoic (Kalimnan): Victoria.
_Hauerina intermedia_, Howchin. Cainozoic (Kalimnan): Victoria.
_Rotalia beccarii_, Linné sp. Pleistocene: Victoria and S. Australia.
_Polystomella striatopunctata_, Fichtel and Moll sp. Pleistocene:
Victoria and S. Australia.
RADIOLARIA.
(?) _Carposphaera_ sp. Lower Cambrian: South Australia.
(?) _Cenellipsis_ sp. Lower Cambrian: South Australia.
_Cenosphaera affinis_, Hinde. Devonian: New South Wales.
_Staurolonche davidi_, Hinde. Devonian: New South Wales.
_Amphibrachium truncatum_, Hinde. Upper Cretaceous: Northern Territory.
_Dictyomitra triangularis_, Hinde. Upper Cretaceous: Northern
Territory.
* * * * *
LITERATURE.
FORAMINIFERA.
Carbopermian.--Howchin, W. Trans. Roy. Soc. S. Austr., vol. XIX. 1895;
pp. 194-198. Chapman, F. and Howchin, W. Mem. Geol. Surv. New
South Wales, Pal. No. 14, 1905. Chapman, F. Bull. Geol. Surv. W.
Austr., No. 27, 1907, pp. 15-18.
Trias.--Chapman, F. Rec. Geol. Surv. New South Wales, vol. VIII. pt.
4, 1909, pp. 336-339.
Jurassic.--Chapman, F. Proc. Roy. Soc. Vict., vol. XVI. (N.S.), pt.
II., 1904, pp. 186-199.
Cretaceous.--Moore, C. Quart. Journ. Geol. Soc., vol. XXVI. 1870, pp.
239 and 242. Howchin, W. Trans. Roy. Soc. S. Austr., vol. VIII.
1886, pp. 79-93. Idem, ibid., vol. XIX., 1895, pp. 198-200. Idem,
Bull. Geol. Surv. W. Austr., No. 27, 1907, pp. 38-43.
Cainozoic.--Howchin, W. Trans. Roy. Soc. S. Austr., vol. XII. 1889,
pp. 1-20. Idem, ibid., vol. XIV. 1891, pp. 350-356. Jensen, H.
I. Proc. Linn. Soc. New South Wales, vol. XXIX. pt. 4, 1905, pp.
829-831. Goddard, E. J. and Jensen, H. I. ibid., vol. XXXII. pt.
2, 1907, pp. 308-318. Chapman, F. Journ. Linn. Soc. Lond. Zool.,
vol. XXX. 1907, pp. 10-35.
General.--Howchin, W. Rep. Austr. Assoc. Adv. Sci., Adelaide Meeting,
1893, pp. 348-373.
RADIOLARIA.
Lower Cambrian.--David, T. W. E. and Howchin, W. Proc. Linn. Soc. New
South Wales, vol. XXI. 1897, p. 571.
Devonian.--David, T. W. E. Proc. Linn. Soc. New South Wales, vol. XXI.
1897, pp. 553-570. Hinde, G. J. Quart. Journ. Geol. Soc., vol.
LV. 1890, pp. 38-64.
Upper Cretaceous.--Hinde, G. J. Quart. Journ. Geol. Soc., vol. XLIX.
1893, pp. 221-226.