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_. [Illustration: =Fig. 91--PALAEOZOIC BIVALVES.= A--Mytilarca acutirostris, Chapm. Silurian. Victoria B--Modiolopsis melbournensis, Chapm. Silurian. Victoria C--Goniophora australis, Chapm. Silurian. Victoria D--Paracyclas siluricus, Chapm. Silurian. Victoria E--Actinopteria australis, Dun. Devonian. New South Wales F--Lyriopecten gracilis, Dun. Devonian. New South Wales ] 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_). [Illustration: =Fig. 92--CARBOPERMIAN BIVALVES.= A--Stutchburia farleyensis, Eth. fil. Carbopermian. N.S. Wales B--Deltopecten limaeformis, Morris sp. Carbopermian. N.S. Wales C--Aviculopecten sprenti, Johnston. Carbopermian. N.S. Wales D--Chaenomya etheridgei, de Kon. Carbopermian. N.S. Wales E--Pachydomus globosus J. de C. Sow. Carbopermian. N.S. Wales ] =Carbopermian Bivalves.--=