Physical Conditions of the Mediterranean Basin. .1.49 



exception of those on Dinas Island, and have a general east-to-west 

 strike with a high dip to the north. Arenig Slates occupy the 

 southern part of the district. Typical Llanvirn Beds with the 

 Placoparia-fa,\ma, occur at Fishguard, and above them the Didymo- 

 graptus Murchisoni-zone of the Lower Llandeilo is found. On this 

 horizon are the first traces of volcanic activity : acid lavas and tuffs 

 are here interhedded with the slates. The Middle Llandeilo is partly 

 faulted out in Goodwick Bay, and near Newport is penetrated by 

 huge intrusive sheets of diabase. The Upper Llandeilo is marked 

 near its base by a thick zone of lava-flows, which are overlain 

 by fossiliferous shales. Hartfell graptolites have been found in the 

 overlying grey and black slates. The lavas and breccias on 

 Strumble Head are held to be on the same horizon as those 

 near Newport. 



All the lavas are acid ; some are soda-potash felsites. Nodular, 

 banded, and perlitic structures are sometimes visible. Crypto- 

 crystalline, microlitic, and micropoikilitic types of groundmass are 

 possessed by these lavas ; the latter type is held to be probably 

 a contact-phenomenon. The intrusive masses consist of diabase, 

 with important tachylytic and variolitic modifications. 



3. ' On the Mean Radial Yariation of the Globe.' By J. Logan 

 Lobley, Esq., F.G.S. 



The author submits considerations (chiefly derived from the 

 characters of the earlier sediments) which lead him to suppose that 

 crust-folds have not been produced by continuous contraction of 

 the Earth, and that the planetary heat and mean radius of the 

 Earth have been practically invarible during the period which has 

 elapsed since Cambrian times. 



February 6th. — Dr. Henry Woodward, F.R.S., President, 



in the Chair. 



The following communications were read : — 



1. ' On Bones of a Sauropodous Dinosaur from Madagascar/ By 

 R. Lydekker, Esq., B.A., F.R.S., V.P.G.S. 



2. ' On the Physical Conditions of the Mediterranean Basin 

 which have resulted' in a Community of some Species of Freshwater 

 Fishes in the Nile and the Jordan Waters.' By Prof. E. Hull, 

 M.A., LL.D., F.R.S., F.G.S. 



The author summarizes the evidence in favour of the existence 

 of barriers in post-Miocene times, separating the Mediterranean 

 area into a chain of basins. He brings forward arguments in 

 support of his contention that the waters of the eastern (Levantine) 

 basin became fresh during a period when the area of evaporation 

 was smaller, and the supply of river-water greater, than at present. 

 Into this freshwater lake the waters of the Nile would flow directly. 

 He has elsewhere given reasons for believing that the Jordan Valley 

 from Lake Huleh to Arabah was the bed of a lake over 200 miles 



