The earliest known trilobites in Australia are some Cambrian species from South Australia, Western Australia, Victoria, and Tasmania.

Fig. 108—CAMBRIAN TRILOBITES.

A—Ptychoparia howchini, Eth. fil. L. Cambrian. South Australia
B—Dolichometopus tatei, H. Woodw. L. Cambrian. South Australia
C—Agnostus australiensis, Chapm. Up. Cambrian. Victoria
D—Ptychoparia thielei, Chapm. Up. Cambrian. Victoria
E—Dikellocephalus florentinensis, Eth. fil. L. Cambrian. Tasmania

Lower Cambrian Trilobites.—

In the Lower Cambrian Limestone of Yorke Peninsula, South Australia, the following trilobites occur:—a species doubtfully referred to Olenellus (? O. pritchardi); Ptychoparia howchini ([Fig. 108 A]); P. australis; Dolichometopus tatei ([Fig. 108 B]); and Microdiscus subsagittatus. The Cambrian of the Northern Territory contains Olenellus brownii. In Western Australia Olenellus forresti is found in similar beds.

Upper Cambrian Trilobites.—

The Dolodrook Limestone (Upper Cambrian) of Gippsland, Victoria, contains the remains of the primitive little trilobite Agnostus (A. australiensis, Fig. 108 C); Crepicephalus (C. etheridgei); and Ptychoparia (P. thielei ([Fig. 108 D]) and P. minima). The Upper Cambrian sandstones of Caroline Creek, Tasmania, contain Dikellocephalus (D. tasmanicus); a species of Asaphus and Ptychoparia (P. stephensi). Beds of the same age in the Florentine Valley, Tasmania, have yielded Dikellocephalus (D. florentinensis, Fig. 108 E).

Ordovician Trilobites.—

Trilobites of Lower Ordovician age or even older, are found in the Knowsley beds near Heathcote in Victoria. They are referred to two genera, Dinesus and Notasaphus. Both forms belong to the ancient family of the Asaphidae. Associated with these trilobites are some doubtful species of sea-weed, spicules of siliceous sponges, traces of threadlike hydrozoa, some fragments of graptolites allied to Bryograptus, and several brachiopods. At the Lyndhurst Gold-fields, near Mandurama, New South Wales, trilobites related to the genus Shumardia have been found associated with brachiopods (lamp-shells), pteropods (sea-butterflies), and graptolites (hydrozoa) of an Upper Ordovician facies.