1846.] PRESTWTCH ON THE ISLE OF WIGHT TERTIARIES. 



235 



nism of these non- fossil if erous beds, and for limiting this subdivision 

 to the lower portion only of the Alum Bay section, will be shown more 

 fully in treating of stratum " c?." 



In the meantime I beg to refer to the accompanying sections. 



The first of these (2) is a general section of the Paris basin, 

 viewed with reference to the maximum development of marine con- 

 ditions in the lower groups, as being the conditions approximating 

 the most closely to tliose of the Hampshire basin. In this diagram 

 the divisions are taken from Brongniart and Cuvier, D'Archiac, 

 Constant Prevost, Ch. d'Orbigny, &c., and the strata are repre- 

 sented of the average thickness on a scale of one inch to a hundred 

 feet. 



3. Section between KiNGSCLEEE and HuNGERFORD*. 



Chalk. 12 3 4,5 6 



The next diagram, No. 3, drawn on the same scale, shows the 

 extension of the mottled clays, in diminished importance, at the 

 western extremity of the London basin. 



4. Section between Basingstoke and Odiham *. 



Chalk 



Chalk. 



xj: 



5. Section near Hertford*. 



No. 4 shows the same divi- 

 sion in greater thickness at a 

 point in the London basin fur- 

 ther to the east ; while No. 5 

 shows that these beds also 

 range in the northern part of 

 the basin. 



The " lower sands " and the " mottled clays " with the thin over- 



* The references in these diagrams are as follows : — 

 6. Bognor heds. 3. Mottled clays. 



5. Pebble beds ; frequently 2. Sand. 



with ironsand. 1. Conglomerate of flints, green and 



4. Sands (light-coloured). ochreous sand. 



The Bognor beds in (3) consist of brown and dark clays with Panopcea inters 

 media, Pectunculus brevirostris and Dentalium planum. In (4) they are brown 

 or reddish clays, and contain Pholadomya margaritacea, Vermetus lioffiioreims 

 and Dentalium planum. In (5) they are brown sandy clays with Pectuncnltis 

 brevirostris and Panopaa intermedia. 



It seems proved by the distinct superposition of these beds that all of them arc 

 of the same age ; namely, that of the lower group in the Isle of Wight. 



