326 Reports and Proceedings — 



replaced by crystalline calcite ; they are embedded in a matrix of 

 granular limestone. 



As a general rule the sponge-spicules are inclosed in a compact 

 matrix in which their forms can only be partially studied, but under 

 certain conditions they are loosely distributed in sand, or in fine 

 powder in cavities in chert, from whence they can be obtained quite 

 free from matrix. The sponge-beds appear to be wholly composed 

 of detached, free, spicules; entire sponges are absent. These spicules 

 belong to numerous species. All four orders of siliceous sponges are 

 represented, but those of Monactinella and Hexactinella sponges 

 form but a small proportion, while those of Tetractinella and Lithi- 

 stid sponges, more particularly of the Megamorina family, are 

 extremely abundant. 



II. — Geological Society of London. 

 I.— May 13, 1885.— Prof. T. G. Bonney, D.Sc, LL.D. T.E.S., 



President, in the Chair. — The following communications were read : 



1. " On the Ostracoda of the Purbeck Formation ; with Notes on 

 the Wealden Species." By Prof. T. Enpert Jones, F.E.S., F.G.S. 



The author stated that in 1850 Prof. Edward Forbes had deter- 

 mined the tripartite division of the Purbeck beds, after working at 

 the sections in the south of England with Mr. Bristow, and had inti- 

 mated that several species of the so-called " Cypridee " aided him in 

 arriving at this result. He did not, however, publish any account 

 of the several forms, and we know of his intended species only (1) 

 by his having pointed them out to his friends Messrs. Bristow, 

 Osmond Fisher, and W. Cunnington ; (2) by a letter to Mr. Bristow 

 in 1851 and one to the author in 1854; (3) by some diagrams in the 

 Museum of Practical Geology ; and (4) by some rough woodcuts in 

 Sir Charles Lyell's 'Manual of Elementary Geology,' 5th edition 

 (1855). Having a large collection of Purbeck and Wealden Ento- 

 mostraca, the author has endeavoured to decide which w^ere E. 

 Forbes's species ; and from a careful examination of the collections 

 in the Geological Society's Museum, the Museum of Practical 

 Geology, and the British Museum, in which he has been greatly as- 

 sisted by Mr. E. T. Newton, F.G.S., and Mr. C I). Sherborn, he has 

 arrived at the definite conclusion that there are fourteen species in 

 E. Forbes's three divisions of the Purbeck series. Five of them 

 (Cypris pm-beclcensis, Candona hononiensis, C. ansata, Cythere Blalcei, 

 and C. vetirugata) occur only in the Lower Purbeck ; and of the 

 others, six occur in both the Middle and Upper. Of the fourteen, 

 five {Cypridea valdensis, very rare in the Purbeck, C. tnhercidata, C. 

 Dunheri, Cyprione Bristovii, and Darwinella leguminella) go up into 

 the Wealden from the Middle and Upper divisions only. Cypridea 

 punctata for the Upper, C. granulosa {fasciculatn) for the Middle, 

 and Cypris purheckensis for the Lower Purbeck, seem to be always 

 characteristic. 



2. "Evidence of the Action of Land-ice at Great Crosby, Lanca- 

 shire." By T. Mellard Eeade, Esq., F.E.S. 



The author pointed out that the Triassic rocks under the Low- 



