26 Dr. Wright oti the Geology of the Isle of Wight. 



tion. It is traversed by seams of small flint pebbles and by six 

 or seven layers of septaria. At the mouth of the ravine is a 

 hard brown clay, the equivalent of the brown clay which rises 

 near Beacon Bunny in the Hordle section. It contains the same 

 shells, but they are at Alum Bay in the form of casts. I observed 

 in one block, Nucula, Venericardia, Oliva and Plevrotoma. It 

 contains much iron and three layers of septaria. The next por- 

 tion is the true representative of the Barton clay. It is very 

 fossiliferous, but the shells are much crushed and fragile. It 

 is traversed by a layer of septaria and seams of small black peb- 

 bles 3 then follows a thick bed of green sand with few shells, 

 which passes into a stiff brown clay containing vast quantities of 

 Nummularia elegans. Tlien succeed beds of green sand with 

 few shells, and six or seven layers of septaria. This bed mea- 

 sures about 300 feet. 



In the following list I have given the Barton shells that are 

 most abundant, but not all the genera and species contained 

 therein : — 



In reviewing the facts disclosed by the study of the preceding 

 section, the following consequences may be logically deduced 

 therefrom : — 



1st. That during the deposition of the series of beds comprised 

 between the upper lacustrine and Barton groups, many alterna- 



