484 
NATURAL HISTORY OF AFRICA, 
furnished at their extremity with an oval mem- 
brane, which serves as a sail. The other six 
arms, or tentaculae, hang over the sides of the 
shell, and are alleged to supply the place of oars 
and rudder. In some places, when the sea is not 
agitated by winds, great numbers of these curi- 
ous animals may occasionally be seen sailing 
about in this manner ; but as soon as the storm 
arises, or any thing disturbs them, they retract 
their tentacula, take in as much water as renders 
them heavier than that in which they swim, and 
sink to the bottom. 
The Cypria monetae or money cowry, is a well 
known species of shell, employed by the natives 
in commerce, instead of money, about 2000 of 
them being esteemed equal in value to a rupee. 
It is a native of the Indian and Adriatic seas.. 
VL — Zoophytes. 
Zoophytes, although the lowest in the scale of 
animated beings, yet are highly interesting in the 
grand and sublime plan of creation. Their num- 
bers exceed all calculation — the minuteness of 
many species is such, that they are not to be dis- 
criminated by the aid of our most powerful mi- 
croscopes — they form one extremity of the zoolo- 
gical scale of magnitude, of which the other is 
occupied with the gigantic whale of the polar re- 
gions. The coral reefs, rocks, and islands of the 
