102 ON THE GEOGRAPHY OF ANIMALS. 
Adanson, who minutely examined and 
described those of the coast round Se- 
negal. The typical volutes, as Voluta 
cymbium, proboscidalis, porcina, Olla 
(fig. 43.), &c., appear to be particu. 
larly plentiful, and lead us to consider 
equinoctial Africa as the metropolis of 
this group, as India is of the cowries 
BAS (Cyprea L.): both these genera, in fact, 
PN are closely allied in affinity ; and both 
are predacious, — feeding solely upon other shell-fish. 
From the western coasts of Africa we also receive 
many other shells, unknown in the Asiatic seas ; such, 
for instance, as the elegant little Marginellas: the 
Harpa sanguinea, or blood-spotted harp ; the Carduum 
costatum, or sharp-ribbed cockle, &c. On the whole, 
the conchology is richer than that of Eastern America, 
but cannot be compared with that of Asia; the genera, 
however, do not materially ditter from such as are com- 
mon to the Red Sea and Persian Gulf. 
(144.) The largest land shells hitherto discovered are 
exclusive natives of these countries, and belong to the 
genus Achatina. ‘There are several varieties, or rather 
species, mostly striped with dark brown on a lighter 
ground, as the Achatina marginata (fig. 44.) *, and ge- 
nerally tinged with a beautiful 
rose colour round their mouth. 
It is highly probable that the 
inhabiting animals, like the large 
slugs of Britain, are carnivo- 
rous ; and they are themselves 
eaten by the natives, and con- 
sidered nutritive and _ whole- 
some. Some of these snails are 
full eight inches long. The 
fluviatile species appear to be 
few, but this may originate 
from their not having been duly 
sought after. Some very large » 
* Swainson, Zool. -Illust. i. pl 30. 
