152 Geological Society : — 



the camptonites. The three types have a different distribution, and 

 do not appear to be connected together by intermediate gradations ; 

 the arnphibole-bearing and the olivine-bearing rocks differ in their 

 mode of occurrence. According to existing analyses, the former 

 range in chemical composition from sub-basic to basic, and the 

 latter from thoroughly basic to ultrabasic. All the rocks have 

 a local stamp, but are probably most nearly related to the camp- 

 tonitic rocks of the Central English Midlands. Intrusion took place 

 at a period not earlier than the Tremadoc, and probably not later 

 than that of the May Hill Sandstone. 



2. ' On the Upper Greensand and Chloritic Marl of Mere and. 

 Maiden Bradley in Wiltshire.' By A. J. Jukes-Browne, Esq., B.A., 

 E.G.S., and John Scanes, Esq. 



The district dealt with is on the borders of Wiltshire and Somerset. 

 The general succession is as follows : — 



Feet. 

 Lower Chalk, with Chloritic Marl at the base ... 200 



Sands with calcareous concretions 3 to 8 



Do. with siliceous concretions (cherts) 20 to 24 



Coarse Greensand 15 



Fine grey and buff sands about 120 



Sandy marlstone 15 



Grey marl and clay (G-ault) 90 



The chert-concretions and the sands in which they occur consist 

 very largely of spicules of lithistid sponges. One of the sandstone- 

 beds' has yielded several species of Necrocarcinus, and may be the 

 chief source of the Crustacea which have been quoted from the 

 Warminster Greensand. Above the chert-beds, and below the horizon 

 at which Stauronema Oarteri comes in, is a variable set of beds which 

 include a layer of concretions known as cornstones or popple- 

 stones. These beds are very rich in fossils, and include at Maiden 

 Bradley a layer of phosphatic nodules. They contain the Bye Hill 

 fauna of the Warminster Greensand, and it is proposed to call them 

 the zone of C atopy g us columbarius. In Southern Wiltshire 

 there is usually a complete passage from this zone into the Chloritic 

 Marl; and as the cephalopoda of this zone are all Chalk-Marl 

 species, the natural inference from the local evidence would be 

 to place the plane of separation between the Selbornian and 

 Cenomanian stages at the base of the C.-colitnibarius beds. In 

 Dorset, however, the break above these beds is so very marked and 

 strong that the authors think that the beds with the Bye Hill fauna 

 must be retained in the Selbornian. It is one of those cases in 

 which the palseontological and the stratigrapbical breaks do not 

 coincide. 



January 9th, 1901.— J. J. H. Teall, Esq., M.A., F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' The Geology of South-Central Ceylon.' By John Parkinson, 

 Esq., E.G.S. 



In this communication the author endeavours to give some 



