386 A NEW CYSTOID (PELMATOZOA, ECHINODERMATA) FROM THE SILURIAN OF NEW SOUTH WALES. By luA A. Brown (Mrs. W. R. Browne). (Plate xxi; two Text-figures.) [Read 27th November, 1963.] Syti02)sis. The paper describes a cystoid (Pelmatozoa, Echinodermata) as a new genus and new species {Austrocystites branagani) from the Upper Silurian near Hatton's Corner, about two miles west of Yass, N.S. Wales. This is the first record of a cystoid from eastern Australia. Intkoduotion. During a geological excursion to the Yass District with other senior students from the University of Sydney in 1949 Mr. (now Dr.) D. F. Branagan found a specimen of a peculiar cystoid which until now has not been critically examined. Although "crinoidal" limestones and fragmentary remains of echinoderms are relatively common in Australia, complete specimens are very rare and there are remarkably few records of fossil Echinodermata, particularly from the Lower Palaeozoic. Recently I have described a new species of Cheirocrinus (Rhombifera, Cystoidea) from the Ordovician of Emanuel Creek, in the Kimberley Division of Western Australia (Brown, 1963) — the first cystoid to be described from Australia — and given references to other recorded occurrences of non-crinoid Pelmatozoa from Australian Palaeozoic rocks, including forms described by Whitehouse (1941), Brown (19416) and Gill and Caster (1960). The Yass specimen to be described was collected from the top of the Dahnanites Bed, west of Hatton's Corner, about a quarter of a mile south of the Yass River and about two miles west of Yass. A map of the area and a description of the Silurian sequence near Yass have already been published (Brown, 1941a). The Dalmanites Bed is a calcareous sandstone, six to ten feet in thickness, whose outcrop forms low scarps and shallow dip-slopes on account of differential erosion. It was called the Phacops Bed by Jenkins (1878a, 18786, 1879) and the Middle Trilobite Bed by Mitchell (1886-1924. See references in Brown, 1941c). It immediately overlies shales containing abundant graptolites, including Monograptus dohemicus, M. nilssoni and others equivalent to the M. nilssoni zone (33) of Great Britain, and is overlain by rocks containing M. sahoeyi of the M. scanicus zone (34) of Great Britain, thus fixing its age as Lower Ludlow (Brown and Sherrard, 1951). The most abundant fossils in the Dalmanites Bed are Dalmanites meridianus Eth. & Mitchell, 1895, and Streptelasma australe (Foerste, 1888), but numerous other trilobites, small brachiopods and other fossils also occur (see list of fossils. Brown, 1941a), including a fragment of an echinoderm collected by Mitchell from his Middle Trilobite Bed in Bowning Village and described by him (Mitchell, 1897) as an echinoid, PalaecMnus sp. (Aust. Museum Specimen, F.28030). Mitchell's specimen contains also fragments of Dalmanites sp. and Streptelasma sp., proving his identification of its stratigraphical horizon, but I doubt his determination of PalaecMnus. It is an external mould of portion of four rows of hexagonal plates of an echinoderm, showing fine ornamentation of granules with some larger tubercles; Proceedings of the Linnean Society of New South Wales, 1963, Vol. Ixxxviii, Part 3.
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