In this paper three new species of trilobites are described from a Lower Silurian horizon at Borenore, near Orange, New South Wales, as Encrinurus borenorensis, Phacops macdonaldi and Dicranogmus bartonensis. The genus Encrinurus Emmrich, 1844, is discussed and it is considered that the genus Gryptonymus Eichwald, 1825, is an abandoned name and cannot be used outside certain limits. Reference is made to the recorded Australian species of the family Lichidae and their geological age. The fossil material was originally found and forwarded to the Australian Museum by Mr. George McDonald, of "Rosyth", Borenore, on whose property the new horizon of fossils is situated. The author visited the locality later and collected additional specimens of all the described species. My thanks are due to Mr. McDonald for his assistance and interest, which have made possible the preparation of this paper. I am also indebted to Mr. F. Booker and Mr. L. Hall, of the Geological Survey of New South Wales, for assistance in determining the geological succession of the area. The trilobite remains are not well preserved and in not one instance was a complete specimen collected. Conditions for their preservation must have been most unfavourable, and it appears as if the trilobites were transported some distance before burial, as the fragmentary remains are found closely packed together in definite zones. The specimens are represented by numerous head-shields and pygidia but, although an intensive search was made, no thoracic segments were found.