THE BEDS AT HEADON HILL AND COLWELL BAY, ISLE OF WIGHT. 85 



9. On the Beds at Headon Hill and Colwell Bat in the Isle of 

 Wight. By H. Keeping, Esq., and E. B. Tawney, Esq., M.A., 

 F.G.S., of the Woodwardian Museum, Cambridge. (Read De- 

 cember 1, 1880.) 



[Plate V.] 

 I. Introduction. 



In a recent communication laid before the Society* the opinion was 

 expressed that a serious error had been made by almost all previous 

 writers in regarding the marine beds at Colwell Bay and Headon 

 Hill as on the same geological horizon ; we read : — " We shall now 

 demonstrate that the Colwell-Bay marine beds are not, as has been 

 hitherto supposed, the equivalent of those of Headon Hill and Hord- 

 well Cliff, but that they occupy a distinct and much higher horizon." 

 Upon the correction of this supposed error a new classification and 

 nomenclature for the Upper Eocene formation of Britain was pro- 

 posed. 



The author further, after a review of the paleeontological evidence, 

 arrived at the conclusion that, on the one hand, the fossils in the 

 Headon Hill and Hordwell Cliffs were identical, while, in the second 

 place, those of Colwell Bay, White Cliff, and Brockenhurst presented 

 the closest agreement among themselves. Then, comparing the 

 former two localities, taken together, with the latter three, taken 

 together, he considered (1) that the fauna of the first group was 

 largely estuarine, and that of the second group marine ; (2) that 

 less than half the forms found in the former occur in the latter ; (3) 

 that the fauna of the former approximated more to that of the Barton 

 beds, having about one third in common with them, while not more 

 than one fifth of those from the latter three localities occur at Barton ; 

 (4) that the fauna of the former two agreed with that of a series of 

 beds on the Continent which underlay and were older than beds 

 containing the fauna of the last three. 



In the following communication the authors attempt to traverse 

 these points in the paper above referred to, in succession. By reference 

 to detail-sections they argue that the stratigraphical evidence is 

 plainly demonstrative of the identity of the Colwell-Bay and Headon- 

 Hill marine series, the beds being continuous through the cliffs and 

 easily traceable. 



Referring to the palaeontological evidence, it is shown from collec- 

 tions, made with their own hands this year, (1) that the fauna of the 

 Colwell-Bay and Headon-Hill beds are identical ; (2) that this fauna 

 differs considerably from that of the Brockenhurst bed, which occupies 

 a lower horizon ; (3) that the Colwell-Bay bed has less than one 

 third of its species common to Barton beds, while the Brockenhurst 

 fauna has nearly one half in common with Barton beds. 



* " On the Oligocene Strata of the Hampshire Basin," by Prof. J. W. Judd, 

 F.R.S., Sec. G-.S., Quart. Journ. Geol. Soc. toI. xxxvi. p. 137. 

 Q. J. G. S. No. 146. H 



