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.—
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]).