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. The limestone beds at Laurie's Creek and other localities in Central Australia contain remains of _Asaphus illarensis_, _A. howchini_ and _A. lissopelta_; whilst in the limestone and quartzite of Middle Valley, Tempe Downs, _A. thorntoni_ also occurs. =Silurian Trilobites.--= [Illustration: =Fig. 109--OLDER SILURIAN TRILOBITES.= A--Ampyx parvulus, Forbes, var. jikaensis, Chapm. Silurian (Melb.) Victoria B--Cypaspis spryi, Gregory. Silurian (Melb.) Victoria C--Homalonotus harrisoni, McCoy. Silurian (Melb.) Victoria D--Phacops latigenalis, Eth. fil. and Mitch. Silurian. N.S. Wales ]