On the so-called Greenstones of Cornwall. 69 



English Channel. As continuity is evident only in the upper 

 division of the Trias, between the area of Devon and Somerset and 

 that of the midland counties, and there is no unconformity in the 

 former, the author maintained that the upper marls, upper sand- 

 stones, and probably the conglomerate and pebble-bed subdivision 

 of Devon and Somerset, are equivalent in time to the Keuper series 

 of the Midland counties, and that deposition took place in Devon 

 and Somerset between Keuper and Bunter times, bridging over the 

 hiatus marked by unconformity in the Midland counties. 



2. " Note on an Os articulare, presumably that of Iguanodon 

 Mantelli." By J. W. Hulke, Esq., F.E.S., F.G.S. 



3. " Description of a new Eish from the Lower Chalk of Dover." 

 By E. Tulley Newton, Esq., F.G.S. 



4. "Further remarks on adherent Carboniferous Producfcidae." 

 By R. Etheridge, jun., Esq., F.G.S. 



5. "The Submarine Forest at the Alt Mouth." By T. Mellard 

 Reade, Esq., F.G.S. 



April 3. — Henry Clifton Sorby, Esq., F.R.S., President, in the 



Chair. 

 The following communications were read : — 



1. " On an Unconformable Break at the base of the Cambrian 

 Rocks near Llanberis." By George Maw, Esq., F.L.S., F.G.S. 



In a paper read before the Society on December 5, 1877 (Q. J. G. 

 S. vol. xxxiv. p. 137), Prof. Hughes referred to an observation 

 made by the author in 1867 as to the occurrence near Llanberis of 

 an unconformable break, indicating the base of the Cambrian, and, 

 while accepting the asserted existence of pre-Cambrian rocks in 

 North Wales, placed the base of the Cambrian in a very different 

 position, and maintained that the appearances described by 

 Mr. Maw might be accounted for by lateral pressure acting upon 

 beds of dissimilar texture and unequal hardness. The author had 

 reexamined the section in question, and maintained his original 

 interpretation of the phenomena, which he regarded as the 

 earliest indication of the existence of a pre-Cambrian series. He 

 accounted for differences observed in the supposed pre-Cambrian 

 rocks at Moel Tryfaen and Llanberis by regarding them as having 

 undergone different degrees of metamorphism. 



2. " On the so-called Greenstones of Central and Eastern Corn- 

 wall." By J. Arthur Phillips, Esq., F.G.S. 



In this paper the author extended his investigations of the rocks 

 formerly mapped as greenstones, from the western (see Q. J. G. S. 

 vol. xxxii. p. 155) into the central and eastern districts of Cornwall. 

 He described in detail various rocks from different parts of these 

 districts, the examination of which had led him to the following 

 conclusions. The numerous lavas which occur here, in addition to 

 the rocks met with in Western Cornwall, arc so interbedded with 

 the slates and schists as to lead to the conviction that they are con- 



