12 



PEOCEEDIN'GS OF THE GEOLOGICAL SOCIETY. [N'OV. 22, 



deposits are utterly devoid of a single organism, and it is not until 

 we descend again to the height of 200 feet above the sea (in Scot- 

 land lower still) that we again begin to find fossils, in beds over- 

 lying the former ; but in the shells of these later beds the glacial 

 character has disappeared altogether." He holds, therefore, that 

 the absence of organic remains from the terraces of Glen Eoy 

 simply accords with the character of similarly placed beds in every 

 other locality, both in Scotland and in Scandinavia. 



NOVEMBEE 22, 1865. 



Eobert Lightbody, Esq., Ludlow, Salop, was elected a Fellow. 

 The following communications were read : — 



1. On some Spaces, formerly occupied hy Selenite, in the Lower 

 EocEKE Clays of the Loistdoi^ Basin ; with remarks on the Oeigij^t 

 and DISAPPEAEA^^CE of the Mineeal. By P. Maetin" Duis'Can', 

 M.B. Lond., Sec. G.S. 



Contents. 



5. Considerations respecting the de- 



posits. 



6. Origin of Selenite. 



7. How it is removed from sedimen- 



tary \_ 



8. Conclusion. 



1. Position of the spaces and impres- 



sions in the Woolwich beds. 



2. Description of the spaces and im- 



pressions. 



3. The mineral condition of the organic 



remains in the beds. 



4. Discovery of the spaces in the Lon- 



don Clay. 



1. Position of the spaces and impressions in the Woolwich beds. 

 — Several sections of the Woolwich beds were made during the 

 formation of the railroad from Lewisham to Dartford, and the 

 Ostrea, Gyrena, and plant-beds were well shown. At one spot, 

 between Mottingham and the Eltham road, the beds had a slight 

 dip to the south-west, and cropped out on the side of a rounded hill 

 which bounds a rivulet to the north. The lowest part of the sec- 

 tion there exposed presented a thick layer of Ostrece, and to this 

 succeeded several feet of light-brown clay, sandy in places, in which 

 Oyrence and Melanioe were very abundant. A plant-bed followed 

 being formed by remains of twigs, leaves, vegetable fibres, and long 

 water-plants. The usual sequence was not then noticed, on the con- 

 trary, several small plant-beds were observed between the succeeding 

 clays. Amidst the clay were some impressions which at first sight re- 

 sembled the markings ofverticillate leaves, but which were evidently 

 parts of spaces once filled by stellate crystals of selenite. 



Several lumps of clay were removed for examination, and pre- 

 sented, when cut into, numerous moulds of entire stellate groups, 

 but all trace of the mineral which had produced them was gone. 



2. Description of the spaces and impressions. — The spaces were from 



