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. [Illustration: =Fig. 93--LOWER MESOZOIC BIVALVES.= A--Unionella carnei, Eth. fil. Triassic. New South Wales B--Mytilus problematicus, Zittel. Triassic. New Zealand C--Monotis salinaria, Zittel. Triassic. New Zealand D--Trigonia moorei, Lycett. Jurassic. W. Australia E--Astarte cliftoni, Moore. Jurassic. W. Australia ] The Queensland Trias (Burrum Formation) contains a solitary species of bivalved mollusca, _Corbicula burrumensis_. This genus is generally found associated with freshwater or brackish conditions. In New Zealand marine Triassic beds occur, containing, amongst other genera, a species of _Leda_. In the succeeding Wairoa Series the interesting fossil, _Daonella lommeli_ occurs. This shell is typical of the Norian (Upper Trias) of the Southern Tyrol. Above the _Daonella_ bed occurs the _Trigonia_ bed, with that genus and _Edmondia_. In the next younger stage, the Otapiri Series, near Nelson, there are fine-grained sandstones packed full of the remains of _Mytilus problematicus_ (Fig. 93 B) and _Monotis salinaria_ (Fig. 93 C), the latter also a Norian fossil. =Jurassic Bivalves.--=