OSBORNE BEDS. 453 



lower horizon than the Venus-bed of Headon Hill (Headon Hill 

 zone). They group the beds as follows : ^ — 



Brockenhurst J Roydon zone. Clays with Volnfa oeniittala about 14 feet. 



Beds. j Biockenhurstzone. 'ia.ndy clays vjiih. Vol lUa suturalis I to 2 ,, 



Prof. Jiidd came to the conclusion that the Colwell Bay Mai-ine Bed and the 

 Brockenhurst Beds were of the same age, but on a higher horizon than the Middle 

 Headon Beds of Headon Hill, etc. His views, however, have not been accepted.* 



Upper Headon Beds. 



The Upper Headon Beds consist principally of clays and sands, 

 yielding freshwater and brackish-water Mollusca. These include 

 Paliiduia lenta, Potamidcs margaritaceiis, Jllelania muricata, Potamomya 

 gtrgaria, Cyrena Wrightii, Corbictda obova/a, and many species found 

 also in the Lower Headon Beds. These beds are seen at Headon 

 Hill, Colwell Bay, etc. At the former locality there are thick and 

 conspicuous beds of limestone with Limncca fusiformis, which thin 

 out towards the north, and are represented by sands and marls in 

 Whitecliff Bay. The thickness of the series is about 50 feet. 



OSBORNE BEDS. 



These Beds, formerly termed the St. Helen's Beds, were named 

 by Prof. Forbes after the Royal demesne of Osborne, near Cowes.* 

 The series consists of red and greenish mottled clays and marls, 

 pale greenish-white limestones, and sandy beds. The beds are 

 from 70 to 100 feet thick, and they are very variable in character. 

 They are well seen east and west of Ryde, in Whitecliff Bay, and 

 at Cliff End, Colwell Bay. They yield Chara Lyellii, Limncca 

 longiscata, Pahidina lenta, Melania excavata, Planorbis (several 

 species), Melanopsis cariyiata, Corbictda obovata, etc. 



Locally the beds were divided as follows by Prof. Forbes : — 



2. The St. Helen''s Sands (named from a place south-east of Ryde), which 

 comprise pale green, yellow, and white sands, hardening into sandstone, 

 with white and yellow marls and clays, having a total thickness of about 

 80 feet. 



I. The NettUstone Grits (named from Nettlestone Point east of Ryde), which 

 include beds of grit, soft sandstone, clay and limestone, having a 

 thickness of about 20 feet. 



1 Q. J. xxxvii. 113 ; Tawney, G. Mag. 1883, p. 157. 



- Judd, Q. J. xxxvi. 137 ; xxxviii. 461 ; H. Keeping and E. B. Tawney, Q. J. 

 xxxvii. 85 ; H. Keeping, G. Mag. 1883, p. 428 ; see also R. Etheridge, Address 

 Geol. Section, Brit. Assoc. 1882; A. S. Lucas, G. Mag. 1882, p. 97 ; O. Fisher, 

 Ibid. p. 138 ; J. W. Elwes, Ibid. 1883, p. 527 ; W. Topley, P. Geol. Assoc, 

 vii. 187. 



^ The beds were grouped by Prof. Judd, together with the Upper Headon Beds, 

 as Lower Bembridge Marls. Q. J. xxxvi. 170; see also Keeping and Tawney, 

 Q. J. xxxvii. 92. 



