98 F. Chapman: 



division ; the rocks overlying tlie Ordovician Ijein^ apparently in 

 all cases referable to the Yeriiigian. Tiiis afFoi-ds us unmistak- 

 able proof of a remarkable overlap of the upper division of the 

 Silurian system in Victoria, the more extensive development of 

 the upper beds being a consequence of the gentle subsidence of 

 the lower or Melbournian rocks during the deposition of the 

 Yeringian mud, sands and shelly accuumlations in the sea which 

 covered central and eastern Victoria during the later Silurian 

 period. 



The uppermost beds of the Yeringian series occurring at 

 Lilydale, in the Upper Y'"arra, near Mount Matlock and at 

 Wombat Creek, contain a few genera (as Panenka, Hercynella^ and 

 Styliola) which are elsewhere more typical of the rocks of 

 Lower Devonian age, as, for example, the Lower Helderberg 

 series of North America. In regard to the latter, it is some- 

 wliat significant that, whilst the European geologists place the 

 L. Helderbergian in the Lower Devonian, the American geologists 

 consider them, together with the Oriskany Sandstone, as the 

 topmost beds of the Silurian, on account of their containing a 

 large percentage of typical Silurian fossils. Our Yei'ingian 

 beds in Victoria seem to furnish a parallel case, for, although the 

 small admixture of Devonian forms has inclined some geologists 

 to denominate them as Siluro-Devonian, their general facies 

 shows them undoubtedly to belong to the highest beds of the 

 ♦Silurian. A systematic examination of the Yeringian bivalves, 

 which the writer iiopes to pul)lish shortly, furnishes further 

 support to the above conclusion. 



Judging by the general aspect of the fo.ssils at Wombat Creek, 

 the mudstones of Bed 4 ai-e probaljly equivalent in part to the 

 Ludlow l)eds of Shropshire, the Upper Oesel Ci'oup in Russia, 

 and the Waterlime Group (and, possibly, the L. Helderberg 

 series) in North America ; whilst the limestone of Bed 3, includ- 

 ing the thick limestone bed at Cave Hill, Lilydale, and the 

 lenticular masses of limestone on the Thomson River, contain a 

 facies which reminds one of the Wenlock Group in England and 

 Scandinavia, and of the Niagara Group of North America. In 

 the present imperfect state of our knowledge of the rich Vic- 



1 This genus also occurs in the Silurian in the Bohemian hasin, but is typically Devonian. 



