FISHES OF THE CHALK. 
131 
by which the death and envelopement of tliese 
animals may be almost simultaneously effected, 
seems therefore necessary to the preservation of 
their remains in the mineral kingdom. Hence 
some naturalists have supposed, that wherever 
petrified fishes occur in considerable numbers, it 
may be inferred that they perished by some sud- 
den catastrophe which destroyed and overwhelmed 
them in shoals, in the very spots where they are 
now found entombed ; this, however, has, probably, 
but seldom been the case. 
Fossil fishes have been found in all the formations 
of England, from the old red sandstone to the ter- 
tiary deposits inclusive. They occur sparingly in 
the chalk of other parts of this island, but in 
Sussex are far from rare, and in the immediate 
vicinity of Lewes have been discovered in a more 
perfect state than in any other locality. 
The specimens are generally distorted ; and but 
few examples have been found, in which the num- 
ber and situation of the fins, and other parts essen- 
tial to the determination of the genus, or species, 
are distinctly exhibited ; yet their general cha- 
racters are sufficiently defined, to prove their want 
of identity with any known existing species. 
The teeth and palates are remarkably beautiful, 
tlieir original substance being heightened by an 
impregmation with iron, and their natural polish 
and sharpness remaining uninjured. The vertebrae 
and other bones are of a reddish brown colour, and 
very friable. 
The fins and scales possess a glossy surface, are 
exceedingly brittle, and both in colour, and in the 
K ‘2 
