J. W. Gregory — Australian Echinoiclea. 491 



OHgocene : as long as we regard these terms as implying only a 

 general homotaxis, they are synonymous with and more convenient 

 than the others. Professor Hutton 1 however assigns his New 

 Zealand Echinoidea to the Cretaceo-Tertiary ; but the fact that more 

 than 20 per cent, of the species from this horizon are still living 

 would appear to conclusively negative this opinion. Prof. Hutton, 

 however, in his latest note, 2 correlates the Cobden with the Ototara 

 limestone, and says that the fossils "indicate an Upper Eocene 

 or Lower Miocene, i.e. an OHgocene age." Prof. Tate's con- 

 clusions 3 are rather intermediate between the two extremes of 

 Prof. M'Coy on the one hand and Prof. Hutton's earlier paper on 

 the other : he correlates the Upper Murravian as Miocene and the 

 Middle Murravian as Eocene. Mr. Dennant 4 again would make the 

 beds older. As the Upper Muddy Creek beds, including Mordillac, 

 contain only 65 per cent, of living species, he assigns them to the 

 OHgocene, and the lower beds with 1*5 per cent, to the Lower 

 Eocene. Nummulites, it may be remarked, also occur on this horizon. 

 The Echinoidea seem to support the views of Mr. Dennant. The 

 presence of so many genera peculiar to or characteristic of the 

 Cretaceous, such as Cavsldulus, Catopygus, Cardiaster, Holaster, and 

 Micraster, and the closer alliance of some species, as H. plauedeclivis, 

 to the Cretaceous rather than the Tertiary representatives of their 

 genera, suggest that the fauna is early Tertiary. 



Some other genera, as Ccelopleurus and Echinolampas, are charac- 

 teristically Eocene, and some peculiar forms have their nearest 

 allies in the same period : further the absence of the typical Upper 

 Tertiary genera is very noticeable ; both of these points strengthen 

 the same conclusion. Moreover, as far as the Echinoidea go, the 

 differences of the faunas of the Upper and Lower Murravian are 

 too slight to allow one to consider them as separated by so long 

 a period as that between the Eocene and the Pliocene ; there is 

 certainly nothing in the Echinoid fauna that would debar the 

 uppermost beds from entering the Oligocene. 



But the real correlation of these beds will depend more on the 

 Mollusca than on the Echinoidea: the latter are so anomalous a 

 collection that little faith can be attached to their evidence on this 

 subject. The interest of the fauna depends on its bearing on other 

 problems. It seems to be composed of two constituents : about 

 a third are species of the ordinary Palasarctic Upper Cretaceous 

 genera ; these seem to have migrated southwards and became 

 mingled on their journey with a fauna that agrees most closely 

 with that of the Eocenes of India and Malaysia. No abyssal types 

 were picked up on the march, nor do any of the species retain any 



1 F. W. Hutton, Q.J G.S. xli. 1885, pp. 558-64. 



2 " On some Fossils lately obtained from the Cobden Limestone at Greymouth," 

 Trans. N. Zealand Inst. xx. 1888, pp. 267-9. 



3 Tate, "Census of the Fauna of the Older Tertiary of Australia," Journ. R. 

 Soc. N. S. Wales, xxii. 1888, pp. 242. 



4 J. Dennant, "Notes on the Muddy Creek Beds, with Brief Remarks on other 

 Tertiary Strata of S. Western Victoria, " Trans. R. Soc. S. Australia, vol. xi. 1889, 

 pp. 53-4. 



