158 Geological Society : — 



the conclusion is drawn that the hypothesis of corrosion is as 

 inapplicable to the latter as to the former. On the contrary, the 

 author believes that the cavities of the spherulites are the result of 

 the hydrous state of the magma. 



March 20th.— J. J. H. Teall, Esq., M.A., V.P.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. 'On a Remarkable Volcanic Vent of Tertiary Age in the 

 Island of Arran, enclosing Mesozoic Eossiliferous Rocks.' 



p ar t j # — ' On the Geological Structure.' By Benjamin Neeve 

 Peach, Esq., E.R.S.L. & E., E.G.S., and William Gunn, Esq., 

 F.G.S. 

 The rocks which form the subject of this paper cover an area 

 of about 7 or 8 square miles, and culminate in Ard Bheinn 

 A'Chruach and Beinn Bhreac. They are in contact with formations 

 ranging from the Lower Old Red Sandstone to the Trias, and are 

 later in date even than the important faults of the area. They are 

 made up partly of fragmental volcanic materials, and partly of various 

 intrusive masses, confined within an almost unbroken ring of intrusive 

 rocks. In addition to igneous fragments, the clastic volcanic rocks 

 contain fragments derived from the surrounding formations ; and 

 also masses of shale, marl, limestone, and sandstone belonging to 

 formations not now found in situ in the island. One of these is 

 several acres in extent, contains fossils, and is in part of Rhaetic 

 age ; a second is a fragment of Lias ; and a third is of limestone and 

 chert resembling the Antrim Cretaceous rocks, and yielding fossils. 

 The absence of Oolitic and older Cretaceous seems to indicate a 

 resemblance between a former succession in Arran and that now 

 seen in Antrim. If these fragments fell into the vent from above, 

 the igneous rocks must be of post-Cretaceous age, and they give an 

 impressive picture of the amount of denudation which has occurred 

 since the period of vulcanicity. 



Part II. — ' Palaeontological Notes.' 

 By E. T. Newton, Esq., E.R.S., E.L.S., F.G.S. 



The masses of Rhsetic strata yield Avicula contorta, Pecten 

 valoniensis, Schizodits (Aainus) chacinus, etc. ; those of Lower 

 Lias Gryplicea arcuata, Ammonites angulatus, and new species 

 of Nuculana and Tancredia, which are figured and described. 

 Thin slices of the Cretaceous limestones prove to be very like those 

 of the Antrim Chalk, and the rocks yield determinable foraminifera, 

 Inocerami, sponges, and echinoderms. 



2. ' On the Character of the Upper Coal Measures of North 

 Staffordshire, Denbighshire, South Staffordshire, and Nottingham- 

 shire ; and their Relation to the Productive Series.' By AValcot 

 Gibson, Esq., F.G.S. 



The Upper Coal Measures of North Staffordshire are capable of 



