Australasian Fossils: A Students' Manual of Palaeontology

Brachiopods are very important fossils in Australasian rocks. They first appear in Cambrian strata, as for example, in the Florentine Valley, in Tasmania, where we find Orthis lenticularis (Fig. 85 A). In Victoria, near Mount Wellington, in the mountainous region of N.E. Gippsland, Orthis platystrophioides is found in a grey limestone. In South Australia the grey Cambrian limestone of Wirrialpa contains the genus Huenella (H. etheridgei). This genus is also found in the Middle and Upper Cambrian of N. America.

Ordovician Brachiopods.—

Coming to Ordovician rocks, the limestones of the Upper Finke Basin in South Australia contain Orthis leviensis and O. dichotomalis. The Victorian mudstone at Heathcote may be of Ordovician age or even older; it has afforded a limited fauna of brachiopods and trilobites, amongst the former being various species of Orthis, Chonetes, and Siphonotreta. The latter genus is represented in both the Lower and Upper Ordovician rocks of slaty character in Victoria (Fig. 85 B).

Silurian Brachiopods.—

The Silurian system in Australasia as in Europe, N. America and elsewhere, is very rich in brachiopod life. It is impossible to enumerate even all the genera in a limited work like the present, the most typical only being mentioned.

In New Zealand the palaeozoic fauna is at present imperfectly worked out, but the following genera from the Wangapekian (Silurian) have been identified, viz., Chonetes, Stricklandinia, Orthis, Wilsonia, Atrypa, and Spirifer. The specific identification of these forms with European types is still open to question, but the species are undoubtedly closely allied to some of those from Great Britain and Scandinavia.

The Victorian Silurian Brachiopods are represented by the horny-shelled Lingula, the conical Orbiculoidea, a large species of Siphonotreta, Stropheodonta (with toothed hinge-line), Strophonella, Chonetes (with hollow spines projecting from the ventral valve, one of the species C. melbournensis being characteristic of the Melbournian division of Silurian rocks), Orthis, Pentamerus, Camarotoechia, Rhynchotrema, Wilsonia, Atrypa (represented by the world-wide A. reticularis), Spirifer and Nucleospira (Figs. 85, 86).

New South Wales has a very similar assemblage of genera; whilst Tasmania possesses Camarotoechia, Stropheodonta and Orthis.

Devonian Brachiopods.—

The Devonian limestones and associated strata are fairly rich in Brachiopods. The Victorian rocks of this age at Bindi and Buchan contain genera such as Chonetes (C. australis), Spirifer (S. yassensis and S. howitti) and Athyris.

In New South Wales we again meet with Spirifer yassensis, veritable shell-banks of this species occurring in the neighbourhood of Yass, associated with a species of Chonetes (C. culleni) (Fig. 86 D, E).

In the Upper Devonian of New South Wales abundant remains occur of both Spirifer disjunctus and Camarotoechia pleurodon (var.).

The Upper Devonian Series at Nyrang Creek near Canowindra, New South Wales, contains a Lingula (L. gregaria) associated with the Lepidodendron plant beds of that locality.

Queensland Devonian rocks contain Pentamerus, Atrypa and Spirifer. In Western Australia the Devonian species are Atrypa reticularis, Spirifer cf verneuili, S. musakheylensis and Uncinulus cf. timorensis.

Carboniferous Brachiopods.—

The Carboniferous Brachiopod fauna is represented in New South Wales at Clarence Town and other localities by a species which has an extensive time-range, Leptaena rhomboidalis var. analoga, and the following, a few of which extend upwards into the Carbopermian:—Chonetes papilionacea, Productus semireticulatus, P. punctatus, P. cora, Orthothetes crenistria, Orthis (Rhipidomella) australis, O. (Schizophoria) resupinata, Spirifer striatus, S. bisulcatus, Cyrtina carbonaria and Athyris planosulcatus.

In New Zealand the Matai series, referred to the Jurassic by Hutton, as formerly regarded by Hector, and latterly by Park, as of Carboniferous age, on the ground of a supposed discovery of Spirifer subradiatus (S. glaber) and Productus brachythaerus in the Wairoa Gorge. Although these species may not occur, the genera Spirifer and Productus are present, which, according to Dr. Thomson, are distinctly of pre-Triassic types.

The Brachiopod fauna of Carbopermian age in New South Wales is rich in species of Productus and Spirifer. Amongst the former are P. cora (also found in Western Australia, Queensland and Tasmania), P. brachythaerus (also found in Western Australia and Queensland), (Fig. 87 A), P. semireticulatus (also found in Western Australia, Queensland and the Island of Timor, and a common species in Europe), and P. undatus (also found in Western Australia and Queensland, as well as in Great Britain and Russia). Strophalosia is an allied genus to Productus. It is a common form in beds of the same age in W. Australia, Tasmania, and New South Wales. The best known species is S. clarkei (Fig. 87 B). This type of shell is distinguished from Productus in being cemented by the umbo of the ventral valve, which valve is also generally less spinose than the dorsal. When weathered the shells present a peculiar silky or fibrous appearance. The genus Spirifer is represented in W. Australia by such forms as S. vespertilio, S. convolutus, S. hardmani, S. musakheylensis, and S. striatus; whilst S. vespertilio and S. convolutus are common also to New South Wales (Fig. 87 C), and the latter only to Tasmania. S. vespertilio is found in the Gympie beds near Rockhampton, Queensland; and S. tasmaniensis in Queensland (Bowen River Coal-field, Marine Series), New South Wales and Tasmania. Of the smoother, stout forms, referred to the sub-genus Martiniopsis, we may mention S. (M.) subradiatus, which occurs in W. Australia, New South Wales, and Tasmania (Fig. 87 D).

In the Queensland fauna, the Gympie series contains, amongst other Brachiopods Productus cora, Leptaena rhomboidalis var., analoga, Spirifer vespertilio and S. strzeleckii.

Other Carbopermian Brachiopod genera found in Australian faunas are Cleiothyris, Dielasma, Hypothyris, Reticularia, Seminula, Cyrtina, and Syringothyris.

Triassic Brachiopods.—

The Kaihiku Series of New Zealand (Hokonui Hills and Nelson) are probably referable to the Trias. The supposed basal beds contain plants such as Taeniopteris, Cladophlebis, Palissya and Baiera. Above these are marine beds containing Brachiopods belonging to Spiriferina, Rhynchonella, Dielasma and Athyris. The succession of these beds presents some palaeontological anomalies still to be explained, for the flora has a decided leaning towards a Jurassic facies.

Next in order of succession the Wairoa Series, in the Hokonui Hills and Nelson, New Zealand, contains Dielasma and Athyris wreyi.

The succeeding series in New Zealand, the Otapiri, or Upper Triassic contains the Brachiopod genera Athyris[3] and Spiriferina, found at Well’s Creek, Nelson.

Jurassic Brachiopods.—

The marine Jurassic beds of W. Australia, as at Shark Bay and Greenough River, contain certain Rhynchonellae allied to European species, as R. variabilis (Fig. 88 A), and R. cf. solitaria.

Lower Cretaceous Brachiopods.—

The Lower Cretaceous or Rolling Downs Formation of Queensland has yielded a fair number of Brachiopods, principally from Wollumbilla,—as Terebratella davidsoni (Fig. 88 B), (?) Argiope wollumbillensis, (?) A. punctata, Rhynchonella rustica, R. solitaria, Discina apicalis and Lingula subovalis. From beds of similar age in Central South Australia and the Lake Eyre Basin Lingula subovalis (Fig. 88 C), and Rhynchonella eyrei have been recorded; the latter has been compared with a species (R. walkeri) from the Middle Neocomian of Tealby in Yorkshire.

Upper Cretaceous Brachiopod.—

A solitary species of the Brachiopoda occurs in the Upper Cretaceous of Australia, namely, Rhynchonella croydonensis (Fig. 88 D) of the Desert Sandstone of the Croydon Gold-fields and Mount Angas, Queensland.

Cainozoic Brachiopods.—

The Brachiopoda of the Cainozoic or Tertiary strata of Australia and New Zealand are well represented by the genera Terebratula, Magellania, Terebratulina, Terebratella, Magasella and Acanthothyris. In the Balcombian or Oligocene of southern Australia occur the following:—Terebratula tateana, Magellania corioensis, M. garibaldiana and Magasella compta (Figs. 89 A, D); and most of these range into the next stage, the Janjukian, whilst some extend even to the Kalimnan. Terebratulina suessi, Hutton sp. (= T. scoulari, Tate) ranges through the Balcombian and Janjukian, but is most typical of the Janjukian beds in Victoria: it also occurs in the Oamaru Series of New Zealand (= Janjukian). Acanthothyris squamosa (Fig. 89 F) is typical of the Janjukian of southern Australia, and it occurs also in the Pareora beds of the Broken River, New Zealand. The latter are green, sandy, fossiliferous strata immediately succeeding the Oamaru stone of the Hutchinson Quarry beds. A. squamosa is said to be still living south of Kerguelen Island. Magellania insolita is a Victorian species which is also found in the Oamaru Series of New Zealand.

Whilst many of the older Tertiary brachiopods range into the next succeeding stage of the Kalimnan in Victoria, such as Magellania insolita, Terebratulina catinuliformis (Fig. 89 E) and Magasella compta, one species, Terebratella pumila, is restricted to the Kalimnan, occurring at the Gippsland Lakes.

The next stage, the Werrikooian, typical in upraised marine beds on the banks of the Glenelg River in western Victoria, contains Magellania flavescens, a species still living (see antea, Fig. 23), and M. insolita, having the extraordinarily wide range of the whole of the Cainozoic stages in southern Australia.

COMMON OR CHARACTERISTIC FOSSILS OF THE FOREGOING CHAPTER.

WORMS.

Eunicites mitchelli, Eth. fil. Silurian: New South Wales.

Oenonites hebes, Eth. fil. Silurian: New South Wales.

Arabellites bowningensis, Eth. fil. Silurian: New South Wales.

Arenicolites sp. Silurian: New South Wales.

Trachyderma crassituba, Chapm. Silurian: Victoria.

Cornulites tasmanicus, Eth. fil. Silurian: Tasmania.

Spirorbis ammonius, M. Edw. var. truncata, Chapm. Mid. Devonian: Victoria.

Spirorbis omphalodes, Goldfuss. Devonian: W. Australia.

Serpula testatrix, Eth. fil. Carbopermian: New South Wales.

Torlessia mackayi, Bather. Lower Mesozoic: New Zealand.

Serpula conformis, Goldfuss. Jurassic: W. Australia.

Serpula intestinalis, Phillips. Lower Cretaceous: Queensland.

Serpula subtrachinus, Eth. fil. Lower Cretaceous: New South Wales.

Serpula ouyenensis, Chapm. Cainozoic: Victoria.

Ditrupa cornea, L. sp. var. wormbetiensis, McCoy. Cainozoic: Victoria.

POLYZOA.

Rhombopora gippslandica, Chapm. Silurian: Victoria.

Fenestella australis, Chapm. Silurian: Victoria.

Protoretepora ampla, Lonsdale. Carbopermian: W. Australia, New South Wales, Queensland, and Tasmania.

Polypora australis, Hinde. Carbopermian: W. Australia.

Rhombopora tenuis, Hinde. Carbopermian: W. Australia.

Rhombopora laxa, Etheridge sp. Carbopermian: Queensland.

Membranipora wilsonensis, Eth. fil. Lower Cretaceous: New South Wales.

(?) Lepralia oolitica, Moore. Lower Cretaceous: Queensland.

Lichenopora australis, MacGillivray. Cainozoic: Victoria.

Heteropora pisiformis, MacGillivray. Cainozoic: Victoria.

Cellaria australis, MacGillivray. Cainozoic: Victoria.

Membranipora macrostoma, Reuss. Cainozoic: Victoria (also living).

Selenaria marginata, T. Woods. Cainozoic: Victoria (also living).

Macropora clarkei, T. Woods sp. Cainozoic: Victoria.

Adeona obliqua, MacGill. Cainozoic: Victoria.

Lepralia burlingtoniensis, Waters. Cainozoic: Victoria.

Bipora philippinensis, Busk sp. Cainozoic: Victoria (also living).

Porina gracilis, M. Edwards sp. Cainozoic: Victoria (also living).

Cellepora fossa, Haswell, sp. Cainozoic: Victoria (also living).

Retepora fissa, MacGill. sp. Cainozoic: Victoria (also living).

BRACHIOPODA.

Orthis lenticularis, Wahlenberg sp. Cambrian: Tasmania.

Orthis platystrophioides, Chapm. Cambrian: Victoria.

Huenella etheridgei, Walcott. Cambrian: S. Australia.

Orthis leviensis, Eth. fil. Ordovician: S. Australia, (?) Victoria.

Siphonotreta discoidalis, Chapm. Ordovician: Victoria.

Siphonotreta maccoyi, Chapm. Ordovician: Victoria.

Lingula yarraensis, Chapm. Silurian: Victoria.

Orbiculoidea selwyni, Chapm. Silurian: Victoria.

Chonetes melbournensis, Chapm. Silurian: Victoria.

Stropheodonta alata, Chapm. Silurian: Victoria.

Orthis elegantula, Dalman. Silurian: Victoria.

Pentamerus australis, McCoy. Silurian: Victoria and New South Wales.

Conchidium knightii, Sow. sp. Silurian: Victoria and New South Wales.

Camarotoechia decemplicata, Sow. sp. Silurian: Victoria.

Rhynchotrema liopleura, McCoy sp. Silurian: Victoria.

Atrypa reticularis, L. sp. Silurian: New South Wales and Victoria. Devonian: New South Wales, W. Australia and Queensland.

Spirifer sulcatus, Hisinger sp. Silurian: Victoria.

Nucleospira australis, McCoy. Silurian: Victoria.

Chonetes australis, McCoy. Mid. Devonian: Victoria.

Chonetes culleni, Dun. Mid. Devonian: New South Wales.

Spirifer yassensis, de Koninck. Mid. Devonian: New South Wales and Victoria.

Spirifer cf. verneuili, de Kon. Mid. Devonian: New South Wales and W. Australia.

Lingula gregaria, Eth. fil. Upper Devonian: New South Wales.

Spirifer disjunctus, Sow. Up. Devonian: New South Wales.

Productus cora, d’Orb. Carboniferous: New South Wales and Queensland.

Orthothetes crenistria, Sow. sp. Carboniferous: New South Wales.

Spirifer striatus, Sow. Carboniferous: New South Wales.

Productus brachythaerus, Sow. Carbopermian: New South Wales, Queensland, W. Australia.

Strophalosia clarkei, Eth. sp. Carbopermian: New South Wales, Tasmania and W. Australia.

Spirifer (Martiniopsis) subradiatus, Sow. Carbopermian: New South Wales, Tasmania and W. Australia.

Spirifer convolutus, Phillips. Carbopermian: New South Wales, Tasmania and W. Australia.

Cleiothyris macleayana, Eth. fil. sp. Carbopermian: W. Australia.

Dielasma elongata, Schlotheim sp. Trias (Kaihiku Series): New Zealand.

Athyris wreyi, Suess sp. Trias (Wairoa Series): New Zealand.

Athyris sp. Trias (Otapiri Series): New Zealand.

Rhynchonella variabilis, Schlotheim sp. Jurassic: W. Australia.

Terebratella davidsoni, Moore. Lower Cretaceous: Queensland.

Rhynchonella solitaria, Moore. Lower Cretaceous: Queensland.

Lingula subovalis, Davidson. Lower Cretaceous: Queensland and S. Australia.

Rhynchonella croydonensis, Eth. fil. Upper Cretaceous: Queensland.

Terebratula tateana, T. Woods. Cainozoic (Balcombian and Janjukian): Victoria and S. Australia.

Magellania corioensis, McCoy, sp. Cainozoic (Balcombian and Janjukian): Victoria and S. Australia.

Magellania garibaldiana, Davidson sp. Cainozoic (Balcombian and Janjukian): Victoria and S. Australia.

Magasella compta, Sow. sp. Cainozoic (Balcombian to Kalimnan): Victoria and S. Australia.

Terebratula suessi, Hutton sp. Cainozoic (Balcombian and Janjukian): Victoria, S. Australia, and New Zealand (Oamaru Series.)

Acanthothyris squamosa, Hutton sp. Cainozoic (Janjukian): Victoria and S. Australia, New Zealand (Oamaru Series) (also living).

Terebratella pumila, Tate. Cainozoic (Kalimnan): Victoria.

Magellania flavescens, Lam. sp. Pleistocene: Victoria (also living).

LITERATURE.

WORMS.

Silurian.—Etheridge, R. jnr. Geol. Mag., Dec. III. vol. VII. 1890, pp. 339, 340. Idem, Proc. Roy. Soc. Tas. (for 1896), 1897, p. 37. Chapman, F. Proc. R. Soc. Vict., vol. XXII. (N.S.), pt. II. 1910, pp. 102-105.

Devonian.—Hinde, G. J. Geol. Mag., Dec. II. vol. VII. 1890, p. 199. Chapman, F. Rec. Geol. Surv. Vict., vol. III. pt. 2, 1912, p. 220.

Carboniferous.—Etheridge, R. jnr. Bull. Geol. Surv. W. Australia, No. 10, 1903, p. 10.

Carbopermian.—Etheridge, R. jnr. Mem. Geol. Surv. New South Wales. Pal. No. 5, 1892, pp. 119-121.

Lower Mesozoic.—Bather, F. A. Geol. Mag., Dec. V. vol. II. 1905, pp. 532-541.

Lower Cretaceous.—Etheridge, R. jnr. Mem. Soc. Geol. Surv. New South Wales, Pal. No. 11. 1902, pp. 12, 13.

Cainozoic.—Chapman, F. Proc. R. Soc. Vict., vol. XXVI. (N.S.) pt. I. 1913, pp. 182-184.

POLYZOA.

Silurian.—Chapman, F. Proc. R. Soc. Vict., vol. XVI. (N.S.), pt. I. 1903, pp. 61-63. Idem, Rec. Geol. Surv. Vic., vol. II., pt. 1, 1907, p. 78.

Carboniferous.—Hinde, G. J. Geol. Mag. Dec. III. vol. VII. 1890, pp. 199-203.

Carbopermian.—De Koninck Mem. Geol. Surv. New South Wales, Pal. No. 6, 1898, pp. 128-140.

Cainozoic.—Stolicka, F. Novara Exped., Geol. Theil., vol. I. pt. 2, pp. 87-158. Waters, A. W. Quart. Journ. Geol. Soc., vol. XXXVII. 1881, pp. 309-347; ibid., vol. XXXVIII. 1882, pp. 257-276 and pp. 502-513; ibid., vol. XXXIX. 1883, pp. 423-443; ibid., vol. XL. 1884, pp. 674-697; ibid., vol. XLI. 1885, pp. 279-310; ibid., vol. XLIII. 1887, pp. 40-72 and 337-350. MacGillivray, P. H. Mon. Tert. Polyzoa Vict., Trans. Roy. Soc. Vict., Vol. IV. 1895. Maplestone, C. M. “Further Descr. Polyzoa Vict.,” Proc. Roy. Soc. Vict., vol. XI. (N.S.), pt. I. 1898, pp. 14-21, et seqq.

BRACHIOPODA.

Cambrian.—Tate, R. Trans. R. Soc. S. Austr., vol. XV. 1892, pp. 185, 186. Etheridge, R. jnr. Rec. Austr. Mus., vol. V. pt. 2, 1904, p. 101. Walcott, C. D. Smiths. Misc. Coll., vol. LIII. 1908, p. 109. Chapman, F. Proc. R. Soc. Vic., vol. XXIII. (N.S.), pt. I. 1911, pp. 310-313.

Ordovician.—Etheridge, R. jnr. Parl. Papers, S. Aust., No. 158, 1891, pp. 13, 14. Tate, R. Rep. Horn Exped., pt. 3, 1896, pp. 110, 111. Chapman, F. Rec. Geol. Surv. Vict., vol. I. pt. 3, 1904, pp. 222-224.

Silurian.—McCoy, F. Prod. Pal. Vic. Dec. V. 1877, pp. 19-29. Eth., R. jnr. Rec. Geol. Surv. New South Wales, vol. 3, pt. 2, 1892, pp. 49-60 (Silurian and Devonian Pentameridae). Idem, Proc. Roy. Soc., Tas., (for 1896), 1897, pp. 38-41. De Koninck, L. G. Mem. Geol. Surv. New South Wales, Pal. No. 6, 1898, pp. 20-29. Dun, W. S. Rec. Geol. Surv. New South Wales, vol. VII. pt. 4, 1904, pp. 318-325 (Silurian to Carboniferous). Ibid., vol. VIII. pt. 3, 1907, pp. 265-269. Chapman, F. Proc. R. Soc. Vict., vol. XVI. (N.S.), pt. 1, 1903, pp. 64-79. Ibid., vol. XXI. (N.S.), pt. 1, 1908, pp. 222, 223. Ibid., vol. XXVI. (N.S.) pt. 1. 1913, pp. 99-113.

Devonian.—McCoy, F. Prod. Pal. Vict., Dec. IV., 1876, pp. 16-18. Foord, A. H. Geol. Mag., Dec. III. vol. VII. 1890, pp. 100-102. Etheridge, R. jnr. Geol. and Pal. Queensland, 1892, pp. 64-68. De Koninck, L. G. Mem. Geol. Surv. New South Wales, Pal., No. 6, 1898, pp. 64-85. Chapman, F. Proc. R. Soc. Vict., vol. XVIII. (N.S.), pt. 1, 1905, pp. 16-19.

Carboniferous.—Etheridge, R. jnr. Rec. Austr. Mus., vol. IV. No. 3, 1901, pp. 119, 120. Idem, Geol. Surv. W. Austr., Bull. No. 10, 1903, pp. 12-23. Dun, W. S. Rec. Geol. Surv. New South Wales, vol. VII., pt. 2, 1902, pp. 72-88 and 91-93.

Carbopermian.—Sowerby, G. B., in Strzelecki’s Phys. Descr. of New South Wales, etc., 1845, pp. 275-285. McCoy, F. Ann. Mag. Nat. Hist., vol. XX. 1847, pp. 231-236. Foord, A. H. Geol. Mag. Dec. III. vol. VII. 1890, pp. 105 and 145-154. Etheridge, R. jnr. Geol. and Pal. Queensland, 1892, pp. 225-264. De Koninck, L. G. Mem. Geol. Surv. New South Wales, Pal., No. 6, 1898, pp. 140-203. Dun, W. S. Rec. Geol. Surv. New South Wales, vol. VIII. pt. 4, 1909, pp. 293-304.

Lower Cretaceous.—Moore, C. Quart. Journ. Geol. Soc., vol. XXVI. 1870, pp. 243-245. Etheridge, R. jnr. Mem. R. Soc. S. Austr., vol. II. pt. 1, 1902, pp. 8, 9.

Upper Cretaceous.—Etheridge, R. jnr. Geol. and Pal. Queensland, 1892, p. 560.

Cainozoic.—McCoy, F. Prod. Pal. Vict., Dec. V. 1877, pp. 11-13. Tate, R. Trans. R. Soc. S. Austr., vol. III. 1880, pp. 140-170. Idem, ibid., vol. XXIII. 1899, pp. 250-259. Hutton, F. W. Trans. N.Z. Inst., vol. XXXVII. 1905, pp. 474-481 (Revn. Tert. Brach.).

CHAPTER X.

FOSSIL SHELL-FISH (MOLLUSCA).

Molluscan Characters.—

The phylum or sub-kingdom Mollusca is a group of soft-bodied animals (mollis, soft), which, although having no external skeleton, usually possess the protective covering of a shell. This shell is secreted from the outer skin or mantle, and is composed of carbonate of lime (calcareous) with a varying proportion of organic material.

Hard Parts.—

Fossil molluscan remains consist practically of the shells, but the calcareous apertural lid (operculum) of some kinds is often preserved, as in Turbo and Hyolithes; or the horny lids of others, as Bithynia of the European Pleistocene “brick earths.” The cuttle-fishes have hard, horny beaks and internal bones, and the latter are frequently found fossil in Australia.

Characters of Pelecypoda.—

The class for first consideration is the important one of the Bivalved Mollusca, the LAMELLIBRANCHIATA (“plate-gills”) or PELECYPODA (“hatchet foot”). The shells are double, hinged dorsally and placed on either side of the animal, that is, they are left and right. The height is measured on a vertical line drawn from the beaks or umbones to the ventral margin. The length is the greatest distance between the margins parallel with a line drawn through the mouth and posterior adductor impression. The thickness is measured by a line at right angles to the line of height. The shell being placed mouth forward, the valves are thus left and right. The anterior is usually shorter, excepting in some cases, as in Donax and Nucula.

Hinge Structure.—

In the absence of the animal, the character of the hinge-structure is very important. Some are without teeth (edentulous). The oldest forms have been grouped as the “Palaeoconcha,” and it has been shown that here, although well-developed teeth were absent, the radial ribs of the surface and ventral areas were carried over to the dorsal margin and became a fixed character in the form of crenulations or primitive teeth.

The taxodont type of hinge teeth shows alternating teeth and sockets, as in Nucula.

The schizodont type is seen in the heavy, variable teeth of Trigonia and Schizodus.

The isodont type of hingement is a modification of the taxodont, represented by two ridges originally divergent below the beak, and forming an interlocking series of two pairs of teeth and sockets as in Spondylus; or where the primitive hinge disappears as in Pecten, the divergent ridge-teeth (crura) may only partially develop.

The dysodonts have a feeble hinge-structure derived from the external sculpture impinging on the hinge-line, as in Crenella.

The pantodonta are an ancient palaeozoic group which seems allied to the modern teleodont or long toothed shells, but the laterals may exceed a pair in a single group, as in Allodesma.

The diogenodonta have lateral and cardinal teeth upon a hinge-plate, but never more than two laterals and three cardinals in any one group, as in Crassatellites.

The cyclodonta have extremely arched teeth, which curve out from under the beaks, as in Cardium.

The teleodonts include the more highly developed types of hinge, with attenuated teeth and sockets. Common shells of our coast, and from Cainozoic beds, belonging to this group are Venus, Mactra and Meretrix.

The asthenodonta are boring and burrowing molluscs that have lost the hinge dentition from disuse as Corbula and Pholas.

Cambrian Bivalve.—

The earliest example of a bivalved shell in Australian rocks is Ambonychia macroptera (Fig. 90 A), which occurs in the Cambrian Limestone of Curramulka, S. Australia. It is quite a small form, being less than a quarter of an inch in length.

Ordovician Bivalve.—

In the basal Ordovician mudstone of Heathcote, Victoria, there is a bivalve which in some respects resembles a Modiolopsis (?M. knowsleyensis), but the exact relationship is still doubtful.

Silurian Bivalves.—

The Silurian sandstones, mudstones, slates and limestones of Australia and New Zealand, unlike the older rocks just mentioned, contain a rich assemblage of bivalve fossils. In Victoria the lower division or Melbournian stage contains the following principal genera:—Orthonota, Grammysia, Leptodomus, Edmondia, Cardiola, Ctenodonta, Nuculites, Nucula, Palaeoneilo, Conocardium, Modiolopsis and Paracyclas. The upper division or Yeringian stage contains other species of similar genera to those in the Melbournian, as Grammysia, Palaeoneilo and Conocardium; whilst Panenka, Mytilarca, Sphenotus, Actinodesma, Lunulicardium, Actinopteria and Cypricardinia are, so far as known, peculiar to this and a still higher stage. Cardiola is a widely distributed genus, occurring as well in Tasmania; whilst in Europe it is found both in Bohemia and Great Britain. Its time-range in the northern hemisphere is very extensive, being found in beds ranging from Upper Ordovician to Devonian. Actinopteria is found also in New South Wales and New Zealand, and Pterinea and Actinodesma in New South Wales.

The molluscs with a taxodont hinge-line (beset with numerous little teeth and sockets) are quite plentiful in the Australian Silurian; such as Nucula, a form common around Melbourne (N. melbournensis (Fig. 90 D)); Nuculites, which has an internal radial buttress or clavicle separating the anterior muscle-scar from the shell-cavity, and which is found likewise in the Melbourne shales (N. maccoyianus (Fig. 90 E)); Ctenodonta, represented in both the Melbournian and Yeringian stages (C. portlocki); and Palaeoneilo, a handsome, subrostrate generic type with concentric lamellae or striae, commonest in the Melbournian, but occasionally found in the younger stage (P. victoriae Fig. 90 F, Melbournian;—P. raricostae, Yeringian). Conocardium is represented by two species in Victoria (C. bellulum and C. costatum); whilst in New South Wales C. davidis is found at Oakey Creek. In New Zealand Actinopteria and Pterinea occur in the Wangapeka series (Silurian).

Devonian Bivalves.—

The compact limestone and some shales of Middle Devonian age in the N.E. Gippsland area in Victoria, contain several as yet undescribed species belonging to the genera Sphenotus, Actinodesma and Paracyclas.

The genera Paracyclas, Aviculopecten and Pterinea have been recorded from New South Wales, chiefly from the Yass district. The derived boulders found in the Upper Cretaceous beds forming the opal-fields at White Cliffs, New South Wales, have been determined as of Devonian age. They contain, amongst other genera, examples of Actinopteria (A. australis), Lyriopecten (L. gracilis) (Fig. 91 F), and Leptodesma (L. inflatum and L. obesum).

One of the most prolific palaeozoic series for bivalved mollusca is the Carbopermian. To select from the numerous genera and species we may mention Stutchburia farleyensis (Fig. 92 A) and Edmondia nobilissima from Farley, New South Wales; and Deltopecten limaeformis (Fig. 92 B), found in the Lower Marine Series at Ravensfield, New South Wales, and in the Upper Marine Series at Burragorang and Pokolbin in the same State, in Queensland at the Mount Britton Gold-field, and in Maria Id., Tasmania. Deltopecten fittoni occurs in both series in New South Wales, and in the Upper Marine Series associated with “Tasmanite shale” in Tasmania. Aviculopecten squamuliferus is a handsome species found alike in Tasmania and New South Wales; whilst A. tenuicollis is common to W. Australia and New South Wales. Other characteristic bivalves of the Carbopermian of New South Wales are Chaenomya etheridgei (Fig. 92 D) and Pachydomus globosus (Fig. 92 E). The gigantic Eurydesma cordatum is especially characteristic of the New South Wales Lower Marine Series, and is also found in Tasmania. All three species are found in Queensland.

Triassic Bivalves.—

The Triassic rocks of New South Wales were accumulated under either terrestrial, lacustrine, or brackish (estuarine) conditions. Hence the only bivalved mollusca found are referred to the freshwater genera Unio (U. dunstani) and Unionella (U. bowralensis and U. carnei (Fig. 93 A)). The latter genus differs from Unio in the structure of the adductor muscle-impressions.