42 Reporta and Proceedings — Geological Sociefi/ of London. 



The greater number of the sponges described were discovered 

 by Mr. T. S. Hall, M.A., of Melbourne University, in incoherent 

 detrital beds of Eocene age, in the southern part of Victoria ; a few- 

 were picked out of some washings of fragniental polyzoa from 

 the same district and horizon, by Mr. B. W. Priest. Some of 

 the specimens are in an extremely perfect condition, and their 

 structural details are as distinctly shown as in recent sponges. 

 They are also of more than local interest in that they are the first 

 fossil forms described of a group of calcisponges, the Lithonina, 

 characterized by the peculiar aberrant forms of some of the spicules, 

 and the mode in which they are closely fitted and organically fused 

 together to form the skeletal mesh. This structure has, so far, 

 only been recognized in one recent species, Petrosiroma Schulzei, 

 Diiderlein, from the Japanese Sea. 



The sponges are small, unattached, with a glassy, firm, resistant 

 skeleton, calling to mind that of siliceous Lithistida. They are 

 built up of a great variety of spicular forms ; some are simple rods, 

 with three- and four-rayed spicules, similar to those in recent 

 calcisponges ; but the majority ai-e aberrant four-rayed forms, with 

 three of the rays curved and with obtuse or expanded ends which, 

 are clasped, and fused as well, to the surfaces of adjacent spicules. 

 The connected spicules form continuous anastomosing or radial 

 fibres resembling those in the fossil Pharetrones, to which they are 

 in some other respects similar, and it is probable that the spicules in 

 the fibres of some members of this family were likewise organically 

 cemented together. The common Forosphcerce from the Upper 

 Chalk, generally regarded as Hydrocorallines allied to the recent 

 Millepora, are also closely related to the above sponges, and the 

 author hopes shortly to publish the evidence for their affinity to 

 this group. 



The Victorian sponges are placed in four new species, belonging 

 to three genera: two of these are new; the other, Bactronella, Hinde, 

 was founded on some peculiar calcisponges of Jurassic age, now 

 known to be Lithonine in character. 



2, " The Silurian Sequence of Ehavader." By Herbert Lapworth, 

 Esq., F.G.S. ^ y 1 ' 



This paper opens with a general reference to the Ordovician and 

 Silurian complex of Central Wales, and a notice of the geological 

 work hitherto done in the region. The stratigraphical relations of 

 the Silurian formations which occur in the country surrounding 

 the town of Rhayader (Radnorshire) are then described in detail. 

 Typical and confirmatory sections are given, demonstrating the 

 complete local sequence of the rocks of the Rhayader district. These 

 are illustrated by lists of characteristic graptolites. These fossils 

 are compared with those of Southern Scotland, Sweden, and North 

 Wales, showing that the graptolite succession is everywhere similar, 

 and fixing the age of the Rhayader Series as representing the Lower 

 Llandovery, Upper Llandovery, and Tarannon of other areas. 

 Finally, several new species of Climacograjjtus and Diplograptus 

 are described. 



