Mr. C. Moore on Secondary Deposits. 69 



proved by reference to the sections at Cwrt, near Langan, at St. 

 Mary Hill Common, west of Tyrmynydd, and at the Stormy Cement- 

 works, where it immediately overlies the Rhsetic series ; while its 

 palseontological affinity with the Lias is proved by the occurrence 

 throughout its entire thickness of the most characteristic shells of 

 that formation, viz. Gryphcea incurva, Ostrea liassica, Lima gigantea, 

 and Ammonites. 



These conglomeratic strata extend over a large area from Sutton 

 to beyond Cowbridge ; and wherever the Lias rests upon Carboni- 

 ferous Limestone or Magnesian Conglomerate, it assumes an ab- 

 normal lithological character, and becomes more or less conglome- 

 ratic. The replacement, in this district, of the ordinary calcareous 

 and argillaceous sediments of which the Rhsetic and Liassic series 

 are usually composed, in the former case by sandstones, and in the 

 latter by conglomerates., indicates that they are the near-shore and 

 shallow-water deposits of an area that now forms part of South 

 Wales, and which was partially undergoing slow depression during 

 the deposition of the Lias. 



After noticing the occurrence of lead-ore (Galena) in these beds, 

 the term Lias Conglomerate, originally applied to them by Sir Henry 

 De la Beche, was proposed as being sufficiently precise and di- 

 stinctive, the name Infra-lias, by which they are sometimes denoted, 

 being objected to as being both vague and misleading. 



5. " On Abnormal conditions of Secondary Deposits when con- 

 nected with the Somersetshire and South Wales Coal-basins ; and 

 on the age of the Sutton and Southerndown series." By Charles 

 Moore, Esq., F.G.S. 



The author first described the geological constitution of the 

 Mendip Hills, which, in his opinion, were upheaved by the intrusion 

 of a basaltic dyke (now noticed for the first time) during the period 

 of the Upper Trias. The Mendip chain proved an island barrier to 

 the incursion of the deeper sea-deposits of the south, on which lived 

 the Microlestes and other terrestrial animals. Along the south side 

 of this barrier shore-deposits were formed, the " Carboniferous Lime- 

 stone " constituting the floor of the ocean at that time. 



He then instituted a comparison between the Rha?tic and Liassic 

 formations within and those without the Somersetshire coal-basin. 

 The thickness of the beds, from the Trias to the Inferior Oolite, was 

 stated to be, outside the coal-field, 3320 feet, whilst inside it was 

 only 169 feet. These results were obtained from an examination of 

 numerous sections, which were described in detail by the author. 



After considering the horizontal deposits beyond the Mendips, 

 and the unconformable conditions within the coal-basin, the author 

 discussed the abnormal conditions which are presented by deposits 

 of the same age when they are intimately connected with the "Car- 

 boniferous Limestone." In the Charterhouse Lead-mine a deposit 

 of clay 12 feet in thickness, and containing Liassic shells, was stated 

 to occur at a depth of 260 feet in the Carboniferous Limestone. 



Among the organic remains, three species of terrestrial shells, 



