CHAP. XI. ] THE ETHIOPIAN REGION. 285 
to introduce, as some writers are disposed to do, a special land 
connection or near approach between Madagascar and all these 
countries, independently of Africa; except perhaps in the case 
of the Malay Islands, as will be discussed further on. 
Land-shells— Madagascar and the adjacent islands are all’ 
rich in land-shells. The genera of Helicide are Vitrina, Helix, 
Achatina, Columna (peculiar to Madagascar and West Africa), 
Buliminus, Cionella (chiefly Oriental and South American, but 
not African), Pupa, Streptaxis, and Succinea. Among the Oper- 
culata we have T'runcatella (widely scattered, but not African) ; 
Cyclotus (South American, Oriental, and South African) ; Cyclo- 
phorus (mostly Oriental, with a few South African) ; Leptopoma 
(Oriental); Megalomastoma (Malayan and South American) ; 
Inthidion (peculiar to Madagascar, Socotra, and South-West 
Arabia) ; Otopoma (with the same range, but extending to West 
India and New Ireland) ; Cyclostomus (widely spread but not 
African) ; and Omphalotropis (wholly Oriental and Australian). 
We thus find the same general features reproduced in the land- 
shells as in the insects, and the same remarks will to a great 
extent apply to both. The classification of the former is, how- 
ever, by no means so satisfactory, and we have no extensive 
and accurate general catalogues of shells, like those of Lepi- 
doptera and Coleoptera, which have furnished us with such 
valuable materials for the comparison of the several faunas. 
On the probable Past History of the Ethiopian Region. 
Perhaps none of the great zoological regions of the earth 
present us with problems of greater difficulty or higher 
interest than the Ethiopian. We find in it the evidence of 
several distinct and successive faunas, now intermingled; and it 
is very difficult, with our present imperfect knowledge, to form 
an adequate conception of how and when the several changes 
occurred. There are, however, a few points which seem suffi- 
ciently clear, and these afford us a secure foundation in our 
endeavour to comprehend the rest. 
Let us then consider what are the main facts we have to 
account for.—1. In Continental Africa, more especially in the south 
