THE OLIGOCENE SERIES 561 



Bembridge Group. The lower beds of this group \v -re 

 separated by Professor Forbes in 1853, under tin- name of the St. 

 Hrlt-ns Beds, afterwards changed to " ( Mmi-ne lleds." In the 

 Memoirs of the Geoloyirnl l<umy they are described as a separate 

 fjroiip, luit as tlu- tonsils they contain arc not distinctive, and are all 

 "t tn -.-1 1 water species, they are certainly not entitled to rank as a 

 stage. Professor Judd and Mr. H. Keeping group them with the 

 t'verlyin-j IVmbridge Beds under the name of Lower Bembridge 

 marls,* 1 and if this is adopted the Bembridge Group will consist 

 of three members, as below: 



Wliitecliff. 



Hamstead 

 and Headon. 



3. Upper marls ..... 75 106 



2. Bembridge Limestone ... 15 25 



1. Lower marls or Osborne Beds 74 80 



164 211 



The Lower or Osborne Marls at Headon Hill and Colwell Bay 

 con>ist of white, blue, and red marls with calcareous concretions 

 which contain Limncea longiscata, Planorbis discus, Viviparus lentus, 

 and other freshwater shells. At Whiteclift" Bay they consist of 

 dark-green clays and sands, but are much concealed by landslips, 

 and the best sections occur along the north-eastern coast from 

 Osborne to Nettlestone Point ; here, however, they assume a very 

 different facies, the lower 20 feet consisting of marls, with bauds of 

 , hard yellowish sandy ragstone and shell limestone full of Viviparus 

 lentus and Melania excavata, the upper 50 feet consisting of green 

 and yellow sands alternating with marls and clays, containing 

 Melania excavata, Planorbis obtusus, Limncea longiscata, and Cyrence. 



The Bembridge Limestone is a cream-coloured stone with inter- 

 >i rat i tied marls ; sometimes it is compact, sometimes quite tufaceous 

 and concretionary ; it is quarried at Headon Hill, at Sconce near 

 C'liiF End, and at Binstead near Ryde, and it is also exposed at 

 Bembridge Point and in Whitecliff Bay. Its contents are terrestrial 

 and freshwater, many species of Helix, Amphidromus, Achatina, 

 Glandina, Cyclotus, Clausilia, Limneea, Planorbis, and Viviparus 

 occurring, with oviform bodies which are supposed to be the eggs 

 of the large Amphidromus ; steins and seeds of Chara are common, 

 and mammalian remains are found in the Binstead quarries. 



The Upper Bembridge Marls extend from the river Yar to 

 Bembridge and Foreland Point, and occupy some space round 

 Osborne, Ryde, and St. Helens. At Hamstead they consist 

 entirely of freshwater beds, chiefly blue and green clays contain- 

 ing Viviparus lentus, Melania acuta, Potamaclis turritissima, 

 Melanopsis carinata, Cyrena semistriata, and C. pulchra. 



2o 



