156 
CHALK MARL. 
composes the constituent substance of the fossils, 
the calcareous spar occurs in the fissures and cavi- 
ties in the marl. The organic remains found in these 
pits are very numerous ; they consist of several 
species of ammonites^ nautili, turi'iUtes, scaphites, 
hamites, the teeth and vertebras of sharks, &c. 
Offham Pit. This excavation lies on the road- 
side, between Offham and Cooksbridge, to the east 
of‘ the road near the seat of Thomas Partington, 
Esq. ; it produces ammonites, nautili, turrilites, 
scaphites, &c. 
Clayton, near Hurstperpoint. A marl pit at this 
place has afforded to the researches of Mr. Weekes, 
turrilites, hamites, ammonites, scaphites, &c. 
In other localities of the marl, the fossils are less 
abundant than in those above enumerated, and the 
turrilites, hamites, and scaphites but rarely occur. 
On the surface, a narrow belt of this deposit ap- 
pears to encircle Lewes Levels, separating the latter 
from the edge of the chalk hills : this want of con- 
tinuity, however, does not extend beneath the sur- 
face : the marl is invariably found upon sinking 
through the alluvial clay, of which the Levels are 
composed. Protrusions of the marl through the 
clay occur in some situations, and these form islands 
when the levels are inundated ; a circumstance that, 
previously to the improved state of the navigation 
of the Ouse, was of very frequent occurrence. 
MINERALS. 
The mineralogical productions of tlie grey marl 
are few, and offer but little variety : they consist of 
