LIMESTONES FORMED BY ORGANISMS.—Organic limestones constitute by far the most important group of fossiliferous rocks. Rocks of this class are composed either wholly of carbonate of lime, or contain other mineral matter also, in varying proportion. Many kinds of limestones owe their origin directly to the agency of animals or plants, which extracted the calcareous matter from the water in which they lived in order to build their hard external cases, as for example the sea-urchins; or their internal skeletons, as the stony corals. The accumulated remains of these organisms are generally compacted by a crystalline cement to form a coherent rock.

The chief groups of animals and plants forming such limestone rocks are:—

(a) FORAMINIFERA.—Example. Foraminiferal limestone as the Nummulitic limestone of the Pyramids of Egypt, or the Lepidocyclina limestone of Batesford, near Geelong, Victoria (Fig. 43).

(b) CORALS.—Ex. “Madrepore limestone,” or Devonian marble, with Pachypora. Also the Lilydale limestone, with Favosites, of Silurian age, Victoria (Fig. 44).

(c) STONE-LILIES.—Ex. Crinoidal or Entrochial limestone, Silurian, Toongabbie, Victoria (Fig. 45). Also the Carboniferous or Mountain limestone, Derbyshire, England.

(d) WORM-TUBES.--Ex. Serpulite limestone of Hanover, Germany. Ditrupa limestone of Torquay and Wormbete Creek, Victoria.

(e) POLYZOA.—-Ex. Polyzoal limestone, as the so-called Coralline Crag of Suffolk, England; and the Polyzoal Rock of Mount Gambier, S. Australia.

(f) BRACHIOPODA.—Ex. Brachiopod limestone of Silurian age, Dudley, England. Orthis limestone of Cambrian age, Dolodrook River, N. E. Gippsland.

(g) MOLLUSCA.—Ex. Shell limestone, as the Turritella bed of Table Cape, Tasmania, and of Camperdown, Victoria (Fig. 46), or the Purbeck Marble of Swanage, Dorset, England.

(h) OSTRACODA.—Ex. Cypridiferous limestone, formed of the minute valves of the bivalved ostracoda, as that of Durlston, Dorset, England (Fig. 47).

(i) CADDIS FLY LARVAE.—Ex. Indusial limestone, formed of tubular cases constructed by the larvae of the Caddis fly (Phryganea). Occurs at Durckheim, Rhine District, Germany.

(j) RED SEAWEEDS.—Ex. Nullipore limestone, formed by the stony thallus (frond) of the calcareous sea-weed Lithothamnion, as in the Leithakalk, a common building stone of Vienna.

(k) GREEN SEAWEEDS.—Ex. Halimeda limestone, forming large masses of rock in the late Cainozoic reefs of the New Hebrides (Fig. 48).

(l) (?) BLUE-GREEN SEAWEEDS.—Ex. Girvanella limestone, forming the Peagrit of Jurassic age, of Gloucester, England.

Section IV.—CARBONACEOUS and MISCELLANEOUS ROCKS.

COALS and KEROSENE SHALES (Cannel Coal).—These carbonaceous rocks are formed in much the same way as the deposits in estuaries and lagoon swamps. They result from the sometimes vast aggregation of vegetable material (leaves, wood and fruits), brought down by flooded rivers from the surrounding country, which form a deposit in a swampy or brackish area near the coast, or in an estuary. Layer upon layer is thus formed, alternating with fine mud. The latter effectually seals up the organic layers and renders their change into a carbonaceous deposit more certain.

When shale occurs between the coal-layers it is spoken of as the under-clay, which in most cases is the ancient sub-soil related to the coal-layer immediately above. It is in the shales that the best examples of fossil ferns and other plant-remains are often found. The coal itself is composed of a partially decomposed mass of vegetation which has become hardened and bedded by pressure and gradual drying.

Spore coals are found in thick deposits in some English mines, as at Burnley in Yorkshire. They result from the accumulation of the spores of giant club-mosses which flourished in the coal-period. They are generally referred to under the head of Cannel Coals. The “white coal” or Tasmanite of the Mersey Basin in Tasmania is an example of an impure spore coal with a sandy matrix (Fig. 49).

The Kerosene Shale of New South Wales is related to the Torbanite of Scotland and Central France. It occurs in lenticular beds between the bituminous coal. It is a very important deposit, commercially speaking, for it yields kerosene oil, and is also used for the manufacture of gas. The rock is composed of myriads of little cell-bodies, referred to as Reinschia, and first supposed to be allied to the freshwater alga, Volvox; but this has lately been questioned, and an alternative view is that they may be the megaspores of club-mosses (Fig. 50).

The coals of Jurassic age in Australia are derived from the remains of coniferous trees and ferns; and some beautiful examples of these plants may often be found in the hardened clay or shale associated with the coal seams.

The Brown Coals of Cainozoic or Tertiary age in Australia are still but little advanced from the early stage, lignite. The leaves found in them are more or less like the present types of the flora. The wood is found to be of the Cypress type (Cupressinoxylon). In New Zealand, however, important deposits of coal of a more bituminous nature occur in the Oligocene of Westport and the Grey River Valley, in the Nelson District.

BONE BEDS.—The bones and excreta of fish and reptiles form considerable deposits in some of the sedimentary formations; especially those partly under the influence of land or swamp conditions. They constitute a kind of conglomerate in which are found bone-fragments and teeth (Fig. 51). These bone-beds are usually rich in phosphates, and are consequently valuable as a source of manure. The Miocene bone-bed with fish teeth at Florida, U.S.A., is a notable example. The nodule bed of the Victorian Cainozoics contains an assemblage of bones of cetaceans (whales, etc.).

BONE BRECCIAS.—These are usually formed of the remains of the larger mammals, and consist of a consolidated mass of fragments of bones and teeth embedded in a calcareous matrix. Bone-breccias are of frequent occurrence on the floors of caves which had formerly been the resort of carnivorous animals, and into which they dragged their prey. The surface water percolating through the overlying calcareous strata dissolved a certain amount of lime, and this was re-deposited on the animal remains lying scattered over the cave floor. A deposit so formed constitutes a stalagmite or floor encrustation. As examples of bone-breccias we may refer to the limestone at Limeburners Point, Geelong (Fig. 52); and the stalagmitic deposits of the Buchan Caves.

IRONSTONE.—Rocks formed almost entirely of limonite (hydrated peroxide of iron) are often due to the agency of unicellular plants known as diatoms, which separate the iron from water, and deposit it as hydrous peroxide of iron within their siliceous skeletons. In Norway and Sweden there are large and important deposits of bog iron-ore, which have presumably been formed in the beds of lakes.

Clay ironstone nodules (sphaerosiderite) have generally been formed as accretions around some decaying organic body. Many clay ironstone nodules, when broken open, reveal a fossil within, such as a coprolitic body, fern frond, fir-cone, shell or fish.

Oolitic ironstones are composed of minute granules which may have originally been calcareous grains, formed by a primitive plant or alga, but since replaced by iron oxide or carbonate.

The Tertiary ironstone of western Victoria is found to contain leaves, which were washed into lakes and swamps (Fig. 53); and the ferruginous groundmass may have been originally due to the presence of diatoms, though this yet remains to be proved.

PART II.—SYSTEMATIC PALAEONTOLOGY.

CHAPTER V.

FOSSIL PLANTS.

Cambrian Plants.—

The oldest Australian plant-remains belong to the genus Girvanella. This curious little tubular unicellular organism, once thought to be a foraminifer, shows most affinity with the blue-green algae (Cyanophyceae), an important type of plant even now forming calcareous deposits such as the calcareous grains on the shores of the Salt Lake, Utah, and the pea-grit of the Carlsbad hot springs. Girvanella problematica occurs in the Lower Cambrian limestones of South Australia, at Ardrossan and elsewhere.

Silurian Plants.—

Amongst Silurian plants may be mentioned the doubtful sea-weeds known as Bythotrephis. Their branch-like impressions are fairly common in the mudstones of Silurian age found in and around Melbourne. They generally occur in association with shallow-water marine shells and crustacea of that period.

The genus Girvanella before mentioned is also found in the Silurian (Yeringian) of Lilydale and the Tyers River limestone, Victoria (Fig. 54).

Haliserites is a primitive plant of the type of the club-mosses so common in the rocks of the Carboniferous period. This genus is found in some abundance in the Yeringian stage of the Silurian in Gippsland (Fig. 55).

Plant-life was not abundant, however, until Upper Devonian and Carboniferous times. In the rocks of these periods we meet with the large strap-shaped leaves of Cordaites and a fern, Sphenopteris, in the first-named series; and the widely distributed Lepidodendron with its handsome lozenge-scarred stems in the later series (Fig. 56). Cordaites has been found in Victoria in the Iguana Creek beds (Upper Devonian), and it also probably occurs at the same horizon at Nungatta, New South Wales. Lepidodendron occurs in the Lower Carboniferous sandstone of Victoria and Queensland (Fig. 57): in New South Wales it is found at Mt. Lambie, Goonoo, Tamworth and Copeland in beds generally regarded as Upper Devonian. Both of these plants are typical of Carboniferous (Coal Measure) beds in Europe and North America. The fern Rhacopteris is characteristic of Upper Carboniferous shales and sandstones near Stroud, and other localities in New South Wales as well as in Queensland (Fig. 58). These beds yield a few inferior seams of coal. Girvanella is again seen in the oolitic limestones of Carboniferous age in Queensland and New South Wales.

Carbopermian Plants.—

The higher division of the Australian Carboniferous usually spoken of as the Permo-carboniferous, and here designated the Carbopermian (see Footnote 2, page 48), is typified by a sudden accession of plant forms, chiefly belonging to ferns of the Glossopteris type. The lingulate or tongue-shaped fronds of this genus, with their characteristic reticulate venation, are often found entirely covering the slabs of shale intercalated with the coal seams of New South Wales; and it is also a common fossil in Tasmania and Western Australia. The allied form, Gangamopteris, which is distinguished from Glossopteris by having no definite midrib, is found in beds of the same age in Victoria, New South Wales, and Tasmania. These plant remains are also found in India, South Africa, South America and the Falkland Islands. This wide distribution of such ancient ferns indicates that those now isolated land-surfaces were once connected, forming an extensive continent named by Prof. Suess “Gondwana-Land,” from the Gondwana district in India (Fig. 59).

Triassic Plants.—

The widely distributed pinnate fern known as Thinnfeldia is first found in the Trias; in the Narrabeen shales near Manly, and the Hawksbury sandstone at Mount Victoria, New South Wales. It is also a common fossil of the Jurassic of South Gippsland, and other parts of Victoria. The grass-like leaves of Phoenicopsis are frequently met with in Triassic strata, as in the upper series at Bald Hill, Bacchus Marsh, and also in Tasmania. The large Banana-palm-like leaves of Taeniopteris (Macrotaeniopteris) are common to the Triassic and Lower Jurassic beds of India: they are also met with in New Zealand, and in the upper beds at Bald Hill, Bacchus Marsh.

Jurassic Plants.—

The Jurassic flora of Australasia is very prolific in plant forms. These range from liverworts and horse-tails to ferns and conifers. The commonest ferns were Cladophlebis, Sphenopteris, Thinnfeldia and Taeniopteris. The conifers are represented by Araucarites (cone-scales, leaves and fruits), Palissya and Brachyphyllum (Fig. 60). The Ginkgo or Maiden-hair tree, which is still living in China and Japan, and also as a cultivated plant, was extremely abundant in Jurassic times, accompanied by the related genus, Baiera, having more deeply incised leaves; both genera occur in the Jurassic of S. Gippsland, Victoria, and in Queensland. The Jurassic flora of Australasia is in many respects like that of the Yorkshire coast near Scarborough. In New Zealand this flora is represented in the Mataura series, in which there are many forms identical with those of the Australian Jurassic, and even of India.

Cretaceous Plants.—

An upper Cretaceous fern, (?) Didymosorus gleichenioides, is found in the sandstones of the Croydon Gold-field, North Queensland.

Plants of the Cainozoic.—Balcombian Stage.—

The older part of the Cainozoic series in Australasia may be referred to the Oligocene. These are marine beds with occasional, thick seams of lignite, and sometimes of pipe-clay with leaves, the evidence of river influence in the immediate neighbourhood. The fossil wood in the lignite beds appears to be a Cupressinoxylon or Cypress wood. Leaves referable to plants living at the present day are also found in certain clays, as at Mornington, containing Eucalyptus precoriacea and a species of Podocarpus.

Later Cainozoic deposits, evidently accumulated in lakes, and sometimes ferruginous, may be referred to the Miocene. They are comparable in age with the Janjukian marine beds of Spring Creek and Waurn Ponds in Victoria. These occur far inland and occupy distinct basins, as at the Wannon, Bacchus Marsh (Maddingley), and Pitfield Plains. Leaf-beds of this age occur also on the Otway coast, Victoria, containing the genera Coprosmaephyllum, Persoonia and Phyllocladus. In all probability the Dalton and Gunning leaf-beds of New South Wales belong here. Examples of the genera found in beds of this age are Eucalyptus (a species near E. amygdalina), Banksia or Native Honeysuckle, Cinnamomum or Cinnamon, Laurus or Laurel, and Fagus (Notofagus) or Beech (Fig. 61). In the leaf-beds covered by the older basalt on the Dargo High Plains, Gippsland, leaves of the Ginkgo Murrayana occur.

In South Australia several occurrences of leaf beds have been recorded, containing similar species to those found in the Cainozoic of Dalton and Vegetable Creek, New South Wales. For example, Magnolia Brownii occurs at Lake Frome, Bombax Sturtii and Eucalyptus Mitchelli at Elizabeth River, and Apocynophyllum Mackinlayi at Arcoona.

Fruits of the “Deep Leads.”—

The Deep Leads of Victoria, New South Wales and Tasmania probably begin to date from the period just named, for they seem to be contemporaneous with the “Older Gold Drift” of Victoria; a deposit sometimes containing a marine fauna of Janjukian age. This upland river system persisted into Lower Pliocene times, and their buried silts yield many fruits, of types not now found in Australia, such as Platycoila, Penteune and Pleioclinis, along with Cupressus (Spondylostrobus) and Eucalyptus of the existing flora (Fig. 62).

Pleistocene Plants.—

The Pleistocene volcanic tuffs of Mount Gambier have been shown to contain fronds of the living Pteris (Pteridium) aquilina or Bracken fern, and a Banksia in every way comparable with B. marginata, a species of the Native Honeysuckle still living in the same district.

The siliceous valves of freshwater diatoms constitute the infusorial earths of Victoria, Queensland, New South Wales and New Zealand. The commonest genera met with are Melosira, Navicula, Cymbella (or Cocconema), Synedra, Tabellaria, Stauroneis and Gomphonema. They are, generally speaking, of Pleistocene age, as they are often found filling hollows in the newer basalt flows. In Victoria diatomaceous earths are found at Talbot (See Fig. 42), Sebastopol and Lancefield; in Queensland, at Pine Creek; in New South Wales, at Cooma, Barraba, and the Richmond River; and in New Zealand at Pakaraka, Bay of Islands. In the latter country there is also a marine diatomaceous rock in the Oamaru Series, of Miocene age.

COMMON OR CHARACTERISTIC FOSSILS OF THE FOREGOING CHAPTER.

Girvanella problematica, Nicholson and Etheridge. Cambrian: S. Australia.

Bythotrephis tenuis, J. Hall. Silurian: Victoria.

Haliserites Dechenianus, Göppert sp. Silurian and Devonian: Victoria.

Cordaites australis, McCoy. Upper Devonian: Victoria.

Lepidodendron australe, McCoy. Lower Carboniferous: Victoria and Queensland. Up. Devonian: New South Wales.

Rhacopteris inaequilatera, Göppert sp. Carboniferous: New South Wales.

Glossopteris Browniana, Brongniart. Carbopermian: New South Wales, Queensland, Tasmania and W. Australia.

Gangamopteris spatulata, McCoy. Carbopermian: Victoria, New South Wales and Tasmania.

Thinnfeldia odontopteroides, Morris sp. Triassic: New South Wales. Jurassic: Victoria, Queensland and Tasmania.

Cladophlebis denticulata., Brongn. sp., var. australis, Morris. Jurassic: Queensland, New South Wales, Victoria, Tasmania and New Zealand.

Taeniopteris spatulata, McClelland. Jurassic: Queensland, New South Wales, Victoria, and Tasmania.

(?) Didymosorus gleichenioides, Etheridge fil. Upper Cretaceous: Queensland.

Eucalyptus precoriacea, Deane. Oligocene: Victoria.

Eucalyptus, Banksia, Cinnamomum, Laurus and Fagus. Miocene: Victoria, New South Wales and Tasmania.

Spondylostrobus Smythi, von Mueller. (Fruits and wood). Lower Pliocene: Victoria and Tasmania.

Pteris (Pteridium) aquilina, Linné, and Banksia cf. marginata, Cavanilles. Pleistocene: Victoria and South Australia.

LITERATURE.

Girvanella.—Etheridge, R. jnr. Trans. R. Soc. S. Australia, vol. XIII. 1890, pp. 19, 20. Etheridge, R. and Card, G. Geol. Surv. Queensland, Bull. No. 12, 1900, pp. 26, 27, 32. Chapman, F. Rep. Austr. Assoc. Adv. Sci., Adelaide Meeting (1907), 1908, p. 337.

Devonian Ferns and Cordaites.—McCoy, F. Prod. Pal. Vict. Dec. V., 1876, p. 21. Dun, W. S. Rec. Geol. Surv. New South Wales, vol. V. pt. 3, 1897, p. 117.

Lepidodendron.—McCoy, F. Prod. Pal. Vict., Dec. I. 1874, p. 37. Etheridge, R. jnr. Rec. Geol. Surv, New South Wales, vol. II., pt. 3, 1891, p. 119. Idem, Geol. and Pal. Queensland, 1892, p. 196.

Carboniferous Fungi.—Etheridge, R. jnr. Geol. Surv. W.A., Bull, No. 10, 1903, pp. 25-31.

Carboniferous Ferns.—Dun, W. S. Rec. Geol. Surv. New South Wales, vol. VIII. pt. 2, 1905, pp. 157-161, pls. XXII. and XXIII.

Glossopteris.—Feistmantel, O. Mem. Geol. Surv. New South Wales, Pal. No. 3, 1890. Arber, N. Cat. Foss. Plants, Glossopteris Flora, Brit. Mus., 1905.

Gangamopteris.—McCoy, F. Prod. Pal. Vict., Dec. II. 1875, p. 11.

Jurassic Plants.—McCoy, F. Prod. Pal. Vic., Dec. II. 1875, p. 15. Woods, T. Proc. Linn. Soc. New South Wales, vol. VIII. pt. I. 1883, p. 37. Etheridge, R. jnr. Geol. Pal. Queensland, 1892, p. 314. Dun, W. S. (Taeniopteris), Rep. Austr. Asso. Adv. Sci., Sydney, 1898, pp. 384-400. Seward, A. C. Rec. Geol. Surv. Vic., vol. I. pt. 3, 1904; Chapman, F. Ibid., vol II. pt. 4, 1908; vol. III., pt. 1, 1909. Dun, W. S. Rec. Geol. Surv. New South Wales, vol. VIII. pt. 4, 1909, p. 311.

Older Cainozoic Plants.—McCoy, F. Prod. Pal. Vic., Dec. IV. 1876, p. 31. Ettingshausen, C. von. Mem. Geol. Surv. New South Wales, Pal. No. 2, 1888. Idem, Trans. New Zealand Inst., vol. XXIII. (1890), 1891, p. 237. Deane, H. Rec. Geol. Surv. Vict., vol. I. pt. 1, 1902, pp. 15, 20.

Lower Pliocene Deep Leads.—McCoy, F. Prod. Pal. Vict., Dec. IV. 1876, p. 29. Mueller, F. von. Geol. Surv. Vic., New Veg. Foss., 1874 and 1883.

Pleistocene and other Diatom Earths.—Card, G. W. and Dun, W. S., Rec. Geol. Surv. New South Wales, vol. V. pt. 3, 1897, p. 128.

CHAPTER VI.

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.

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.

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.