PROCEEDINGS OF SOCIETIES. 



Dublin Miceoscopioal Club. 

 IQtl October, 1876. 



Section of ' GherV exhibited, with remarks on its origin. — Pro- 

 fessor Hull, F.E.S., exhibited some thin sections from the upper 

 Chert zone of the Carboniferous limestone which is remarkably 

 persistent throughout the range of that formation from Sligo on 

 the north-west to Co. Carlow on the south-east, and Cork and 

 Kerry on the south-west. These sections, taken from different 

 localities, tended to confirm the opinion of those who believe that 

 the chert is pseudomorphic, and has replaced the limestone of 

 the original rock. Not only are corals and crinoids, which must 

 have originally been formed of carbonate of lime, now frequently 

 found preserved in silica (Chert), but, as these sections showed, 

 obscure traces of these and other forms are brought out with the 

 aid of polarized light, under the microscope. In other cases the 

 sections of corals and crinoids themselves exhibit very beautifully 

 the infiltered silica filling up the interiors of the skeleton, as well 

 as the skeleton itself, of these structures. 



Assuming, then, that the silica has replaced the original calca- 

 reous rock, the question arises at what period this replacement 

 has taken place. Mr. Hull considered it probable that the period 

 was that prior to the deposition of the overlying Yoredale shales, 

 when the organically-formed limestone rock was exjiosed to the 

 waters of the open sea, and was acted upon — first, by waters 

 charged with carbonic acid, followed by others containing silica 

 abundantly in solution. 



Carmine -stained sections of the electric organ and Skin of 

 Malapterurus electricus, were exhibited by Mr. B. Wills Rich- 

 ardson. — Referring to the account given in Cuvier's * Histoire 

 Naturelle des Poissons,' and to Owen's ' Anatomy of the Verte- 

 brates,' Mr. Richardson gave several details of their histology 

 as to which he found these authors, as well as Rudolphi, 

 silent. The skin is beset with numerous beautiful tree-like 

 processes, between which occur short conical processes. These 

 he at first supposed might be fuugoid in nature, though 

 he had afterwards satisfied himself that they were dermal. 



