26o EAST AFRICAN FLORA AND FAUNA part in 



terranean and Red Sea, owing to their being separated in 

 Pliocene times by the whole length of the latter and by most 

 of the Levant. 



The theory has, moreover, the recommendation of throwing 

 considerable light upon the relations of the land and fresh-water 

 faunas of Abyssinia and the adjoining region. The evidence 

 furnished by the fish, which alone we have considered, is fully 

 supported by that obtained from other groups of animals, and 

 also from plants. 



We may take, first, the land and fresh-water shells. The 

 fauna in Abyssinia has long been known to consist of a re- 

 markable combination. The typical African genera, such as 

 Ait her ia^ Iridina, Achatina, Galatea and Lanistes are absent, 

 and the fauna is composed of three distinct elements, all 

 foreign. One group has come from the Cape, another from 

 India, and a third from the north, probably from Palestine. 

 The last group is especially noteworthy. It consists of a 

 group of species which are either still living in Europe, such 

 as the common English pond shells, Lhnncsa pereger, Miill., L. 

 truncatula, Miill, and Succinea debilis, Mor. ; or species that have 

 only just become extinct there, such as Corbicula Jiiuninalis, 

 Mull, which is one of the commonest fossils in the gravels of 

 the Thames valley. This species is still living in the Sea of 

 Galilee, in the Tigris, and also in the Lower Nile. Aubry and 

 Hamon discovered it in 1883 in some old lake beds in the 

 Afar region of Abyssinia, through which the assumed Erythrean 

 River would flow. The shell was found farther south by von 

 Hohnel, and, in the course of a tributary of this river, I found 

 masses forming a shell bed a little to the south of Lake Baringo. 

 There it was associated with Melania tuberculata, Miill., which 

 is another common species in the raised beaches of the Dead 

 Sea. It therefore seems probable that the fauna, which is 

 represented by this Corbicula fluminalis, worked its way into 

 Abyssinia from Palestine, and entered Abyssinia by following 

 the Erythrean River. 



The evidence afforded by the birds and land animals is less 

 complete, because, in consequence of the direct connection with 

 Egypt, the fauna is mainly Mediterranean. But even among 

 the birds there are many species which support the view of the 

 direct connection between Palestine and Eastern Africa. Thus 



