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.

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.

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.

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.

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.