﻿Ordovician Hocks of CaermartJiensJiire. 175 



opposite sides of the anticline. The majority of faults are strike- 

 faults, many of them being thrusts ; these are sometimes so close 

 together that the structure cannot be fully displayed on the 1-inch 

 scale. Cleavage affects the rocks on the northern limb, but is 

 almost absent on the south ; it was induced at a later date than 

 the faulting. The chief igneous rocks are intrusions of diabase ; 

 and there are ashes in the Llanvirn and Llandeilo beds and an ashy 

 shale in the Arenig. 



A description of the entire succession of rocks is given, accompanied 

 by lists of fossils, and each division of importance is followed 

 through its whole extent as shown in the area. In correlating the 

 rocks, it is shown that the Middle and Upper Arenig rocks compare 

 with those of St. David's ; the Llanvirn rocks are very similar, 

 lithologicallv, to the beds of Llanvirn and Abereiddy, and the faunas 

 are practically identical ; the Llandeilo rocks are in the main like 

 those of Pembrokeshire, but the Leptograptus-&W\s\on of the 

 Dicranoc/raptus-Beds closely resembles the Rorrington Flags of 

 Shropshire ; the Bala-Caradoc rocks fall into the divisions already 

 established by Marr & Roberts in an adjoining area ; and the rocks- 

 assigned to the Lower Llandovery are barren of organic remains, as 

 they are elsewhere. 



May 23rd. — R. S. Herries, M.A., Vice-President, 

 in the Chair. 



The following communications were read : — 



1. 'On the Importance of Halimeda as a Reef-forming 

 Organism ; with a Description of the Halimeda-Limestones of the 

 New Hebrides.' By Frederick Chapman, A.L.S., F.R.M.S., and 

 Douglas Mawson, B.E., B.Sc. 



2. ' Notes on the Genera Omospira, Lophospira, and Turrhoma - r 

 with Descriptions of New Species.' By Miss Jane Donald. 



June 13th.— Sir Archibald Geikie, D.C.L., Sc.D., Sec.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. ' Recumbent Folds produced as a Result of Flow.' By 

 Prof. William Johnson Sollas, Sc.D., LL.D., F.R.S., F.G.S. 



Prof. Lugeon, in his treatise on the pre- Alps of Chablais, has de- 

 scribed a series of recumbent folds so greatly exceeding in horizontal 

 extension their vertical thickness, that they are commonly spoken 

 of as sheets rather than folds ; they lie with remarkable flatness 

 one on the other, and, as a rule, those higher in the series extend 



