water from the fhell, in order that it may fwim the more 
readily; then throwing back the two foremoft arms, it 
difplays between them a membrane of wonderful te- 
nuity, which acts as a fail, while with the remaining 
arms it rows itfelf along; the tail in the middle acung 
as a helm to dire its courfe ; and thus purfues its voy- 
age like a little fhip; and if alarmed by any appea- 
rance of danger, takes in the water and defcends.” 
We muft be careful not to confound this fhell, which 
is the real and proper Nautilus, with the chambered 
or pearly Nautilus, which belongs to a very diftin&t 
genus. ‘The Argonauta Argo is found of various fizes, 
from one to fix or cight inches in length, or even 
lager. [t is a native both of the Mediterranean and 
Indian feas. 
