100 
N. spirula ; and the circumstance of the Argonauta being inhabited 
by a mollusca of this class, leave but little doubt that all these shells 
have been the solid appendages of similar animals. 
The representation given by Rumphius, d’ Amboinsche Rar. Tab. 1/, 
Fig. c. of the dead animal of the iV. pompilius, although of an animal 
which was much injured, not only gives the idea of a similar animal, and 
shows the appendage by which it was connected with the siphunculus 
of the shell ; but also seems to bear that figure which authorizes the 
supposition, that part of the shell had been let into the body of the 
animal. This partial envelopement of the shell by the animal is also 
confirmed, as is justly observed by Lamarck, by the blanched appearance, 
which extends some little distance from the edge of the mouth of the 
shell of the N. pompilius, and which differs so widely from that which 
is yielded by the other external part of the shell, which is beautifully 
marked by transverse orange -coloured stripes. 
LXXII. Nautilus. A spiral, many-chambered, discoidal univalve, 
with smooth sides. The turns contiguous, the outer side covering the 
inner. The chambers separated by transverse septa, which are concave 
outwards, and perforated by a tube passing through the disk. 
The different chambers of these shells are very shallow, when com- 
pared with the last, which forms the opening, and which is, doubtless, 
the residence of the animal. 
Whilst examining these shells, it is necessary to pay attention to 
that particular organization, by which a communication is kept up 
between the animal and the most interior part of the shell ; since we 
shall not otherwise be able to judge of the peculiar modifications ot 
these parts, which occur in the fossil remains of this and of other 
genera of this family. 
Some have supposed the siphuncle of the nautilus to have been a 
rigid testaceous tube : thus M. Bose says: “ Toutes ces cloisons sont 
traversees par un petit tuyau cylindrique, epais, creux, imperfore late- 
ralement, qui paroit composoit de petits tuyaux plus evases d’un cott, et 
