chap, xi.] THE ETHIOPIAN REGION. 285 



to introdiice, as some writers are disposed to do, a special land 

 connection or near approach between Madagascar and air 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 Helicidae 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 Truncatclla (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) ; 

 Lithidion (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 



