Geological Society. 179 



case of the Selenocosmiidee, when we do not claim it to be a 

 sign of affinity between the Selenocosmiidee and Idiommata 

 and Trechona. To this it must be replied that Idiommata 

 and Trechona are separated from each other and from the 

 Selenocosmiidse by certain other characters which do not 

 admit of the genera presenting them being grouped in the 

 same category. But the genera of Selenocosmiidee are, apart 

 from the presence of Wood-Mason's organ, much alike in all 

 structural points ; and this, coupled with the fact that they 

 inhabit the same geographical area, lends great weight to 

 the supposition that the mutual possession of Wood- Mason's 

 organ may be regarded as an indication of relationship 

 between them. 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



December 4, 1895.— Dr. Henry Woodward, F.R.S., 

 President, in the Chair. 



The following communication was read: — 



' The Mollusca of the Chalk Pock. —Part I.' By Henry Woods, 

 Esq., M.A., F.G.S. 



In the introductory part of the paper the Author gives an account 

 of the characters, distribution, and literature of the Chalk Pock. 

 Ho points out that the Chalk Pock fauna may be recognized at the 

 same level in Northern France, N.W. Germany, Saxony, Silesia, and 

 Bohemia ; and on account of the wide distribution and distinctive 

 features of this fauna, he suggests that the Chalk Pock merits a 

 palaeontological rather than a lithological designation, and proposes 

 for it the term ' zone of Heteroceras rwssiarwm.' 



The main part of the paper is devoted to the consideration of the 

 cephalopoda, gasteropoda, and scaphopoda ; and is based largely 

 on the collection from Cuckhamsley (B rks) made by the late 

 Mr. Montagu Smith ; but for the loan of many specimens the 

 Author is indebted to Mr. P. M. Brydone, Mr. C. Griffith, Mr. W. 

 Hill, Dr. J. Morison, and Mr. James Saunders. In addition to 

 some genera, of which sufficiently good examples for exact deter- 

 mination have not yet been obtained, the following are repre- 

 sented : — Nautilus, PtycJwceras, Heteroceras, Baculites, Prionocyclus, 

 Pachydiscus, Scaphites, Crioceras, Emarginula, Pleurotomaria, 

 Trochus, Turbo, Crepidula, Natica, Oerithium, Aporrhais, Avellana, 

 and Dentalium. Some new species are described, and the synonymy 

 and distribution of the others treated in detail, figures and descrip- 

 tions being given of the forms not previously well known. The 

 account of the lamellibranchs and the general conclusions are 

 reserved for Part II. 



