284 
ORGANIC REMAINS 
nera, namely, Belemnites^ AmmoniieSy and Nau~ 
tilites. These shells, if we may draw any con- 
clusions from our knowledge of the habits of the 
recent species of the only genus that still exists, 
were indisputably inhabitants of the ocean ; and 
the presence of their remains, in any considerable 
quantity in a formation, affords a fair presumption 
that such formation was a marine deposit. The 
converse of this proposition, we conceive, must 
hold good in a case like the present, where not a 
vestige of these ancient marine genera can be 
traced, among innumerable remains of terrestrial 
vegetables and animals, and of freshwater testa- 
cea. The occasional occurrence of marine remains 
affords no grounds for a contrary opinion, since 
this fact is no more than might be expected under 
such circumstances, and is in strict accordance 
with what may be observed in the deltas and 
estuaries of all great rivers. 
We cannot leave this subject, without offering 
a few genei'al remarks on the probable condition 
of the country through which the waters flowed 
that deposited the strata of Tilgate Forest, and 
on the nature of its animal and vegetable produc- 
tions. Whether it were an island, or a continent, 
may not be determined ; but that it was diversified 
by hill, and valley, and enjoyed a climate of a 
higher temperature than any part of modern Eu- 
rope, is more than probable. Several kinds of 
ferns appear to have constituted the immediate 
vegetable clothing of the soil : the elegant Sphe- 
nopteris, which probably never attained a greater 
height than three or four feet, and the beautiful 
