Reporh and Proceeduujs — Geological Society of London. 189 



Officers :— President : Prof. Charles Lapworth, LL. D.,F.R.S. Vice-Presidents : 

 Sir Archibald Geikie. D.Sc, D.C.L., LL.D., F.R.S. L. &E. ; J. E. Marr, Esq., 

 M.A., F.R.S. ; Professor H. A. Miers, M.A., F.R.S. ; Professor H. G. Seeley, 

 F.R.S., F.L.S. Secretaries: R. S. Herries, Esq., M.A. ; and Professor W. W. 

 Watts, M.A. Foreign Secretary : Sir John Evans, K.C.B., D.C.L., LL.D., 

 F.R.S., F.L.S. Treasurer : W. T. Blanford, LL.D., F.R.S. 



IL— February 26th, 1902.— Prof. Charles Lapworth, LL.D., F.E.S., 



President, in the Chair. The following communications were 

 read : — 



1. "On some Gaps in the Lias." By Edwin A. Walford, Esq., 

 F.G.S. 



The author's endeavour is to prove gaps in the stratigraphical 

 succession of the Lias, involving the removal of zones or parts of 

 zones, and also to prove palceontological gaps by the abrupt appear- 

 ance of many new genera of mollusca. 



The Middle Liassic ferruginous limestone of the zone of Ammonites 

 spinatiis he states to be mainly made up of a kind of crinoid (ferro- 

 crinoid). The zone may be divided into 



2. The Ferrocrinoid hank— upper. 30 feet. 

 1. The Spirifer oxi/ffona heds — lower. 20 feet. 



The upper division varies fi'om 30 feet at an altitude of 700 feet to- 

 6 feet at the altitude of 350 feet on the edges of the Cherwell Vale,. 

 owing to waste by drainage. The upper zone is of great thickness 

 and importance in Oxfordshire and Yorkshire (Cleveland), but almost 

 absent in Dorset, Somerset, and. Gloucestershire, where the fauna of 

 the lower Sjnrifer oxygona beds prevails. The ironstone is thickest 

 towards the escarpment on the west of the Cherwell Vale ; on the 

 east side of the vale it loses both in type and importance. At 

 Bloxham a course of ferruginous limestone is made up of stems of 

 the ferrocrinoid in great part, but near the top it becomes a pink 

 compact limestone, full of fossils of the zone of Ammonites communis : 

 the intermediate transition-bed and zone of Ammonites serpentinus 

 having been removed b}'- inter- waste rather than by contemporaneous 

 erosion. 



x\. transition-bed between the Middle and Upper Lias shows a great 

 incoming of new forms. They are no doubt developed outside lines 

 of known strata. 



A third gap, measured by the occurrence of a thin bed of 

 Pentacrinite-limestone, is in the zone of Ammonites communis. 



The ' spinatus-ironstone ' is believed to lose in thickness on the 

 side of a divide away from the main west-to-east dip. On the 

 Northamptonshire side of the Cherwell, where the slope is to 

 the west, and hence opposite to the general dip, the beds are thin, 

 although the argillaceous beds are better preserved. 



2. " On the Origin of the Eiver-System of South Wales, and its 

 Connection with that of the Severn and Thames." By Aubrey 

 Strahan, Esq., M.A., F.G.S. 



The southerly courses of some rivers from the Usk to the Ogmore 

 are described, and shown to be independent of both the east-and-west 



