226 PROCEEDINGS OP SOCIETIES. 



On the other side of Lough Allen we again come upon the impure 

 limestone, dipping in the same direction. This would seem to indicate 

 a considerable fault in the Lake, — one, I should think, of six or seven 

 hundred feet. 



I have now to point out the principal peculiarity in the section, 

 which is the occurrence here of a bed of gypsum, about five or six feet 

 thick. It is of peculiar appearance, being thickly interspersed with 

 crystals of Selenite, and lies on the impure limestone at the edge of the 

 Lake. I do not know that the occurrence of a bed of gypsum in carbo- 

 nate of lime has been noticed before ; but Professor Jukes informs me 

 that he has seen fossils converted into sulphate of lime, and full of Sele- 

 nite, imbedded in the tertiary limestone of South Australia, and also 

 in the recent limestone of the coral reefs. 



The remainder of the section shows the shale, which is about 120 

 feet thick, and the sandstone which contains the seams of coal worked 

 by the Crevylea Company for their Iron Works. The seat- rock, which 

 corresponds with the under-clay of the English coal-measures, is here a 

 hard, fine-grained sandstone. 



DUBLIN NATUEAL HISTORY SOCIETY. 



FRIDAY EVENING, JUNE 12, 1857. 



Professor W. H. Harvey, M.D., M.R.I.A., F.L.S., President, 

 in the Chair. 



The Minutes having been read and signed, — 



Propessor Kinahan read some notes — 



ON A REMARKABLE VARIETY OF TRICHOMANES RADICANS (KILLARNEY FERn). 



The form of this beautiful and well-known fern, which I lay before your 

 Society to-night, was first brought under my notice by Mr. John Bain, 

 the Curator of the University Botanic Gardens, and is peculiarly inter- 

 esting, as affording an example, among the " Muscoid" ferns, of that 

 form of monstrosity which is met with rather commonly in some genera 

 of our native ferns, and for which I proposed the name of Laciniatum 

 in a paper read before your Society in 1853. The departure from the 

 normal form consists, as there stated, in a depauperation of the mem- 

 branous portions of the frond, the more vascular portions remaining 

 unaltered, and the frond being in consequence generally either scalloped 

 at its edges, or reduced to a linear condition. The fructification is gene- 

 rally absent in this form. 



The causes or conditions which give rise to it are extremely obscure. 

 In Scolopendrium it is generally most prevalent in plants from a dry 

 station, but in Trichomanes I find it prevails in plants from the very 



