A very large number of genera of the Polyzoa have been described from the Tertiary strata of South Australia and Victoria. Some of the principal of these are _Crisia_, _Idmonea_, _Stomatopora_, _Lichenopora_, _Hornera_, _Entalophora_ and _Heteropora_ of the order Cyclostomata; and _Catenicella_, _Cellaria_, _Membranipora_, _Lunulites_, _Selenaria_, _Macropora_, _Tessarodoma_, _Adeona_, _Lepralia_, _Bipora_, _Smittia_, _Porina_, _Cellepora_ and _Retepora_ of the order Cheilostomata. Many of these genera, and not a few Australian species, are found also in the Cainozoic or Tertiary beds of Orakei Bay, New Zealand (Fig. 84). _BRACHIOPODA (Lamp-shells)._ =Brachiopods: Their Structure.--= These are marine animals, and are enclosed in a bivalved shell. They differ, however, from true bivalves (Pelecypoda) in having the shell on the back and front of the body, instead of on each side as in the bivalved mollusca. Each valve is equilateral, but the valves differ from one another in that one is larger and generally serves to attach the animal to rocks and other objects of support by a stalk or pedicle. Thus the larger valve is called the pedicle valve and the smaller, on account of its bearing the calcareous supports for the brachia or arms, the brachial valve. Generally speaking, the shell of the valve is penetrated by numerous canals, which give the shell a punctate appearance. Some brachiopod shells, as _Atrypa_ and _Rhynchonella_, are, however, devoid of these. [Illustration: =Fig. 85--LOWER PALAEOZOIC BRACHIOPODS.= A--Orthis (?) lenticularis, Wahlenberg. Up. Cambrian. Florentine Valley, Tasmania B--Siphonotreta maccoyi, Chapm. Up. Ordovician. Bulla, Vict. C--Lingula yarraensis, Chapm. Silurian. South Yarra, Victoria D--Orbiculoidea selwyni, Chapm. Silurian. Merri Creek, Victoria E--Chonetes melbournensis, Chapm. Silurian. South Yarra, Vict. F--Stropheodonta alata, Chapm. Silurian. Near Lilydale, Vict. ] =Cambrian Brachiopods.--= 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.--=