454 OBSERVATIONS ON THE ANIMALS 
ton, whereto the muscles were attached ; a pouch, in which the ani- 
mal was contained ; and a concamerated shell, to act, probably, like 
that of the Nautilus, and give the possessor a great facility in alter- 
ing its depth in the water, and so of more readily obtaining food 
and avoiding danger. 
It was mentioned just now that one of the parts of the animal 
contained in the horny pouch of this fossil, was known to be a con- 
trivance for secreting and emitting a black fluid, to darken the 
water about it. Now it may fairly enough be asked what proof we 
have of this ; for it must seem a strange thing to one unaccustomed 
to these investigations, that we thus speak positively upon a matter 
which does not, at first sight, seem capable of very clear elucidation. 
Few things, however, can be more clear or certain ; and the reason 
of this will soon appear. 
It is conjectured that at certain periods during the formation of 
the beds of chalky clay called lias, there occurred submarine erup- 
tions, suddenly destroying the lives of vast numbers of animals, and 
burying all together in one heap of mud. At al] events, we occa- 
sionally find various remains of saurians, fish, and other genera of 
lower organisation, so perfectly preserved as to make it evident that 
some very sudden cause of death must have existed to allow of their 
being deposited in that state.* What this cause may have been we 
will not speculate on at present ; but the effects remain, and not the 
least remarkable amongst them must be considered the existence, at 
the present day, of the fragile and destructible ink-pen of a sepia, 
and the very dried fluid itself, capable of being worked up still into 
a good and perfect pigment. We will speak of this horny ink-bag 
and ink a little more in detail ; and since it is very nearly the same 
in the fossil as in the recent state, we might from either describe 
the contrivances, which had clearly the same object in both. 
There is a singular resemblance between the structure of the ink- 
pen in the sepia, and the wing-feather of a bird ; and to this resem- 
blance, it is clear, the name is owing. We find in both a broad 
central shaft, with long narrow filaments transversely placed, and 
extending on each side of the shaft ; but the similarity, of course, 
ceases when we come to internal structure, and is not, indeed, entire 
in the general appearance. 
* I may remark here that it is by no means the case that such sudden de- 
struction will account for the formation of any considerable portions of this 
or any formation. Generally speaking, there is abundant evidence of the 
“i deposition of fossiliferous beds; and the exceptions are rare and very 
ocal. 
