No remains of true Starfishes have been recorded from Australia between the Carbopermian and the Tertiary systems. In the Janjukian Series of Victoria the marginal plates of a species of _Pentagonaster_ are typical fossils. They have been recorded from Waurn Ponds, Spring Creek near Torquay, and Batesford (Fig. 77 D). In the Mallee Bores, both marginal and abactinal plates of this genus are found in polyzoal limestone (Miocene). _Pentagonaster_ also occurs in the Lower Muddy Creek beds (Oligocene), and the Upper beds of the same locality (Lower Pliocene). A species of _Astropecten_ has been described from the Waikari River, New Zealand (Oamaru Series). _OPHIUROIDEA, or Brittle-stars._ =Characters of Brittle-Stars.--= The Brittle-stars are frequently found at the present day cast up on the fine sandy beaches of the coast. They are easily distinguished from true starfishes by having a definite central disc, to which the arms are attached. The arms are used for locomotion and prehension, and have their grooves covered over with plates. The ossicles of the arms are moveable and controlled by muscles which enable them to be used as feet. The lower surface of the disc has a central arrangement of five rhomboidal sets of jaws, formed of modified ossicles, called the mouth frame, whilst the upper surface bears, between one set of arms, the madreporite or covering plate to the water vascular system, as in starfishes. [Illustration: =Fig. 78.--Protaster brisingoides=, Gregory. Negative cast of the calcareous skeleton. Nat. size. Silurian Sandstone, Flemington, Victoria. (_Nat. Mus. Coll._) ] =Silurian Brittle-Stars.--= The Brittle-stars in Australia first appear in the Silurian, but in England and Bohemia date back to the Ordovician. _Protaster_ is the commonest genus, and is represented by _P. brisingoides_ of the Melbournian stage of Silurian strata at Flemington (Fig. 78). It also occurs rarely in the Yeringian beds at Yering, both Victorian localities. A very ornamental form, _Gregoriura spryi_, occurs in the same division of the Silurian at South Yarra. In this fossil the delicate spines attached to the adambulacral ossicles are well preserved and form a marginal fringe to the arm (Fig. 79). _Sturtzura_ is another Silurian genus, found in the Wenlock of England and in the Melbournian of Flemington, Victoria. [Illustration: =Fig. 79.--A Brittle-Star.= (Gregoriura spryi, Chapm.) Nat. size. From the Silurian Mudstone of South Yarra, Victoria. (_Nat. Mus. Coll._) ] =Cainozoic Brittle-Stars.--= From the Victorian Cainozoic beds, in the Lower Pliocene of Grange Burn, Hamilton, a vertebral ossicle of an ophiurian has been obtained, which has been provisionally referred to the genus _Sigsbeia_. _ECHINOIDEA, or Sea-urchins._ This group is an important one amongst Australian fossils, especially those of Cainozoic age.