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.