Cainozoic Regular Echinoids.—
In Australasia they make their first appearance in strata of Tertiary age, and some species, as Paradoxechinus novus, range through Balcombian strata to Kalimnan in Victoria, or Oligocene to Lower Pliocene, but are more typically Janjukian. Echinus (Psammechinus) woodsi ([Fig. 80 B]) is common in Janjukian strata in Victoria and South Australia and occurs sparingly in the Kalimnan. Another common form of the regular Echinoids in Southern Australia is Cidaris australiae ([Fig. 80 A]), ranging from Janjukian to Kalimnan, occurring more frequently in the older series. In New Zealand a species of Cidaris (C. striata), is known from the Oamaru Series at Brighton. An Echinus occurs in the Oamaru Series of Broken River, and two species of that genus in the Wanganui formation of Shakespeare Cliff. Temnechinus macleayana has been recorded from the Cainozoic (Miocene or Pliocene) of Yule Island, Papua.
Irregular Echinoids.—
The irregular Echinoids are not known before the Upper Cretaceous in Australia, and are very common in the Tertiaries. They are distinguished by the anus (periproct) passing backward from the apex, as compared with the regular forms, and by the elongation of the test and the loss of the strong solid spines, which are replaced by thin, slender hair-like spines. The animal is thus better fitted to burrow through the ooze on which it feeds.
Cretaceous Irregular Echinoids.—
An interesting form, Micraster sweeti, is found in the Upper Cretaceous or Desert Sandstone of Maryborough in Queensland, which reminds one of typical European species of this genus.
Cainozoic Irregular Echinoids.—
Amongst the Australian Cainozoic Echinoids of the irregular type the following may be mentioned. The little subglobular test of Fibularia gregata, and Echinocyamus (Scutellina) patella ([Fig. 80 C, D]) are Janjukian in age. The large Clypeaster, C. gippslandicus ([Fig. 80 E]), ranges from the Oligocene to Lower Pliocene in Victoria (Balcombian to Kalimnan), and vies in size, especially in the Janjukian, with some large species like those from Malta and Egypt. This genus includes some of the largest known sea-urchins. The biscuit urchin, Arachnoides (Monostychia) australis, is commonest in the Janjukian, but ranges from Balcombian to Kalimnan. A common urchin from the polyzoal rock of Mt. Gambier is Echinolampas gambierensis, which is also found in the Lower beds of Muddy Creek. A typical Janjukian fossil is Duncaniaster australiae, formerly thought to belong to the Cretaceous genus Holaster. Although found living, the genus Linthia attained its maximum development both in size and abundance, in Janjukian or Miocene times, as seen in L. gigas (having a length of 71/2 inches) and L. mooraboolensis. Echinoneus dennanti is restricted to the Janjukian. Several species of Eupatagus occur in the Cainozoic or Tertiary beds of South Australia, Victoria and New Zealand; Lovenia forbesi ([Fig. 81 C]) is common in the Janjukian to Kalimnan, both in Victoria and South Australia. In the latter State also occur the following genera:—Studeria, Cassidulus, Echinolampas, Plesiolampas, Linthia, Schizaster and Brissopsis. In New Zealand the following Cainozoic genera, amongst others of the irregular sea-urchins, may be cited:—Hemipatagus, Brissopsis, Hemiaster, and Schizaster ([Fig. 81]).
Fig. 81—CAINOZOIC SEA-URCHINS.
