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27 
England, with the exception of Dorset. The only zone that is 
absent is the highest known in England, — Belemnitella 
mucronata; it is only found in Norfolk and Dorset, Hampshire 
and Wilts. Dorset is the only County in England that has all 
the zones of the chalk represented from the highest to the 
Chloritic Marl on the coast. 
Zones of the Chalk. 
UPPER CHALK— 
Zone 1. Belemnitella mucronata. 
Actinocamax ( Belemnitella) quadratus. 
Marsupites. 
Uintacrinus. 
Micraster cor-anguinum. 
Micraster cor-testudinarium. 
MIDDLE CHALK— 
Zone 7. Holaster planus. 
» 8. Terebratulina gracilis, 
», 9. Ehynchonella cuviert. 
LOWER CHALK— 
Zone 10. Actinocamax ( Belemnitella) plenus. 
», 11. Ammonites rotomagensis or Holaster subglobosus. 
», 12. Ammonites varians or Rhynchonella martini, 
Dox we go bo 
The zones of the chalk represented on the Brighton Coast 
and inland to the base of the escarpment to the south of the 
Lewes plain—which is my limit of Brighton and district— 
include all the zones of the chalk from Actinocamax ( Belemni- 
tella) quadratus to the grey chalk, the lowest on the diagram. 
The zone represented on the diagram—AHolaster sub-globosus— 
is the lowest zone found in the Brighton district. The upper 
and middle chalk, which we find to have been deposited in this 
neighbourhood, has been laid down in comparatively deep water. 
This is fairly well proved by the abundance of Ventriculites, 
sponges and the almost total absence of the Gasteropoda. This 
is characteristic of the deep waters of the existing seas and a 
good co-relation with the Cretaceous Sea. I may mention here 
that the Challenger Expedition found mollusca closely allied to 
the cretaceous species at a depth of from 10,000 to 17,000 feet. 
In the upper chalk Univalves are the rarest of fossils ; with great 
depths in the existing seas they are equally rare. In the lower 
chalk they are more frequent, indicating a deposition in a shallower 
sea. The zones are represented by a fossil that has the most 
definitely restricted vertical range. As I explained in the existing 
zones of animal and plant life, the zones are the life histories of 
the species. 
