MOLLUSCOUS ANIMALS. 
483 
and physical distribution. The limited distribu- 
tion of some species of molluscous animals, when 
contrasted with the extensive distribution of 
others, excites the attention of the naturalist, and 
leads him to institute interesting comparisons be- 
tween the external and internal relations of tribes 
of animals, thus already so strikingly marked by 
nature in their geographical and physical distri- 
butions. But this is not the place for discussions 
on these highly curious subjects. We shall now 
notice a few of the species of this class. 
Several species of sepia^ or cuttle-fish, occur on 
the coasts of this continent. Some of them ap- 
pear to be much larger than any of those met 
with on our coasts ; and, if we can credit the ac- 
counts of travellers, some of the African species 
attain a colossal size. 
The animals of the Argonaut tribe are nearly 
allied to the cuttle-iish. The famous nautilus of 
the ancients (the Argonauta argo^ Lin»\ which 
is supposed, in the early ages of the world, to 
have furnished the original idea of navigation, is 
found in the African seas, as in the neighbour- 
hood of the Cape of Good Hope. When it 
means to sail, this animal discharges a quantity 
of water from its shell, by which means it is ren- 
dered lighter than the surrounding medium, and 
of course rises to the surface. Here it extends 
two of its tentacula upwards. These are each 
