102 



ON THE GEOGRAPHY OF ANIMALS. 



Adanson^ who minutely examined and 

 described those of the coast round Se- 

 negal. The typical volutes, as Valuta 

 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 

 {Ct/prcea L.) : both these genera, in fact, 

 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 ditfer 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. lUust. i. pi. 30. 



