Bejjorts and Proceedings — Mineraloijical Society. 41 



" On the Structure and Affinities of the genus Porosphmra, Stein- 

 TOann." By Dr. G. J. Hinde, F.E.S. The well-known rounded and 

 thimble-shaped fossils, of common occurrence in the Chalk of this 

 country, which were named and figured as MiUe2)ora ? globularis 

 and Lunulites urceolata by the late Professor John Phillips, have 

 been, by different authors, referred alternately to Foraminifera, 

 Siliceous Sponges, and Cyclostomate Polyzoa. In 1878 the first- 

 named species was placed by Dr. Steinmann as the type of 

 a separate genus of the Hydrocorallina, which he named Porosjjhcera, 

 and its structure was stated to resemble that of Millepora and 

 Farheria. From an examination of 2,900 specimens collected by 

 Dr. A. W. Kowe and by the author from the diiferent zones of the 

 English Chalk, and of a singularly perfect specimen in flint 

 discovered by Mr. H. Muller, it has been ascertained that the 

 anastomosing fibres of Porosphcera are composed of four- rayed 

 spicules which are fused together so as to form a firm, strong- 

 skeleton. In the form of the spicules and in their mode of union 

 there is the closest resemblance to those of Plectroninia, Hinde, 

 from the Eocene Tertiary of Victoria, Australia, and to the recent 

 Petrostroma, Doderlein, from the Japanese Sea, and with these 

 genera Porosfhcera belongs to the Lithonine group of Calcisponges. 

 The author further discovered fragments of an outer spicular crust or 

 dermal layer on a very few specimens, which consisted of delicate, 

 simple, rod-like, and three-rayed spicules, irregularly agglomerated, 

 but not fused together. It is probable that a similar crust was 

 originally present in all the forms, though it has now to a large 

 extent been removed. 



The following species w^ere recognized and described : P. globu- 

 laris, Phill., P. nuciformis, von Hagenow, P. Woodioardi, Carter, 

 P. pileolus, P. patelliformis, sp.n., and P. arrecta, sp.n. The relative 

 distribution and the range of size of each of these forms in the 

 respective zones of the English Chalk are also given. 



III. — MiNERALOGiOAL SooiETY, November 17th, 1903. — 

 Dr. Hugo Miiller, F.R.S., President, in the chair. Mr. E. H. 

 Solly gave a detailed description of various minerals from the 

 Binnenthal, five of which had not been identified with existing 

 species. These five minerals all contain lead, arsenic, and sulphur, 

 but sufficient material for complete analyses has not yet been 

 obtained. Three of them are red transparent minerals having each 

 one perfect cleavage and a similar vermilion streak, but differing 

 orvstallographically : one is apparently orthorhombic with (100), 

 (flO) = 39° 16', (010), (Oil) = 52° 57', and (001), (101) = 42° 43' ; 

 another is oblique with yS = 78° 46', (100), (101) = 42° 22', and 

 (010), (111) = 37° 3'; while the third has a zone at right angles to 

 the perfect cleavage with angles of approximately 30° and 60°. The 

 other two minerals, which could not be identified with any of the 

 other sulpharsenites of lead previously described by the author, are 

 black with metallic lustre. One of these is oblique with /3 = 81° 11', 



