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LETTER IX. 
MULTILOCULAR SHELLS NAUTILUS FOSSIL SPECIES 
ORTHOCERA. 
We shall now proceed to the examination of the fossil remains of a 
family of shells, which, whether we consider the greatness of their num- 
bers, the peculiarity of their structure, or the little agreement which 
exists between the greater part of them and known recent shells, cannot 
fail strongly to excite our interest and engage our attention. 
These shells are multilocular, being divided into chambers by transverse 
pierced septa : a communication through the septa distinguishing these 
shells from those multilocular shells, which have been just examined. 
Very little is known with respect to the animal which inhabits even 
the recent shells of this description. There is, however, sufficient reason 
for supposing that the animal resides in the last formed chamber of the 
shell, and is of the family Cephalapodes. We are indebted for much of 
this knowledge to M. Peron, who was so fortunate as to obtain the ani- 
mal of Nautilus spiruta in connection with its shell, and brought it, in 
that state, from New Holland. This animal, which appeared to be 
analogous with the sepia, had the shell not only attached to, but so let 
into its posterior extremity , as to leave a pai t of it only in view . 
The near agreement of the internal structure of the shell of N. poni- 
pilius and indeed of most of these many-chambered shells, with that of 
