166 
LECTURE XL 
been supposed by some, that the animal pos- 
sesses the power of at pleasure filling up the 
chambers or cavities either with air or water, or 
of exhausting them of both occasionally, in or- 
der to make itself specifically heavier or lighter, 
during its navigations 5 for this animal is also sup- 
posed to have a power of sailing, though in a less 
perfect manner than the Argonaut or Paper Nau- 
tilus. The animal is also indistinctly allied to the 
Cuttle-Fish tribe ; having an oval body, wdth the 
front or central part furnished with a parrot-shaped 
beak, and surrounded by arms or tentacula ; but 
they differ from those of the Sepise or Cuttles 
in being very short, extremely numerous, disposed 
in several concentric rows or circles, and not be- 
set with any visible suckers. From above the neck 
or round the upper part of the head rises a large, 
concave flap or hood, beset on the inside with nu- 
merous but small suckers or concave tubercles. 
By the elevation and expansion of this concave flap 
or hood the animal of the Pearly Nautilus is sup- 
posed to sail. It is of a pale reddish-purple co- 
lour, with deeper spots and variegations. 
It is remarkable that this animal has also been 
described and figured in the works of Ruinphius, 
but the drawing representing it in its recent and 
