208 Geological Society: — 



stratified rocks. Some limestone pebbles have been perforated by 

 Mollusca and other marine animals. 



The inference drawn by the Author from the facts recorded in his 

 paper is that these weathered boulders once formed portions of 

 moraines on land from which, for a time, the glaciers had receded, 

 and that, after a succession of seasons sufficient to disintegrate these 

 blocks more or less, an increased snowfall caused such an extension 

 of the glaciers that the blocks were carried down to the sea and 

 conveyed away in icebergs and by floating ice to the spots where 

 they are now imbedded. As they occur at different horizons there 

 must have been a repetition of the advance and retreat of the glaciers 

 such as now occurs in Greenland. 



June 10.— Prof. T. G. Bonney, D.Sc, LL.D., F.B.S., President, 

 in the Chair. 



The following communications were read : — 



1. " Note on the Sternal Apparatus in Iguanodon" By J. W. 

 Hulke, Esq., F.B.S., V.P.G.S. 



2. " The Lower Palaeozoic Bocks of the Neighbourhood of Haver- 

 fordwest." By J. E. Marr, Esq., M.A., F.G.S., and T. Boberts, 

 Esq., B.A., F.G.S. 



The authors in this communication described the sequence of the 

 Lower Palaeozoic rocks lying to the north of Haverfordwest and 

 Narberth. Their work is founded on that published by the Geolo- 

 gical Surveyors in their maps, sections, and memoirs. 



To the north of the ridge of rock running eastward from Bock 

 Castle, claimed as Archaean by Dr. Hicks, they have discovered 

 Lingula Flags, with Olenus spinalosus, Wahl, and Agnostus pisi- 

 formis, Linn. These beds are seen underlain by conglomerate, 

 resting upon older rocks, near Trefgarn Bridge. 



South of Dr. Hicks's Archaean ridge, a great fault brings beds of 

 Bala age in juxtaposition with the rocks of the ridge ; hence, in the 

 tract described, no rocks of Tremadoc and true Arenig age have been 

 met with. In the area south of the ridge the rocks are thrown 

 into a complex synclinal, with a complex anticlinal to the south-east, 

 near the town of Narberth. 



The succession which the authors attempted to establish in this 

 area is as follows (in ascending sequence) : — 



i. Didymograptus shales, with Murchisoni-iorm Graptolites. 



ii. Llandeilo limestone, with Asaphus tyrannus, Murch. &c. 



iii. JJicranograptus shales, with Dicranograptus, Climacograptus 

 bicornis, Diplograptus foliaceus, &c, having a zone at the summit 

 marked by the abundance of Orthis argentea, His. 



iv. Bobeston Wathen Limestone, with many corals and Brachio- 

 pods, and few Trilobites. 



v. Trinucleus-seticornis beds, characterized by abundance of 

 Trinucleus seticornis, His., and its variety T. BucMandi. These are 

 subdivided into three stages, viz. : — (a) Sholeshook limestone, with 

 Cystideans and an abundant Trilobite fauna, including Agnostus 



