THYRIDIDAE OF AFRICA AND ITS ISLANDS 21 



M adagascan Zone 



Madagascar (30); Comoro Is (1). 



Seychelles Zone (excluding Aldabra). 



Mane (2) ; La Digue (1) ; Marie Anne (1) ; Silhouette (1) ; Praslin (o) ; Amirantes (o) ; 

 an unspecified island in the group (1). 



Because the collecting, while widespread, has not been as intensive in some areas 

 as in others, the term "apparent endemic" is used in preference to the rather definite 

 term "endemic". In the following discussion, "apparent endemic species" refers 

 to species or subspecies. 



West African Zone 



This zone has 7 apparent endemic species out of a total of 61 species in the area. 

 The faunae of the two countries (Ghana and Nigeria) on each side of the rain-forest 

 gap (Dahomey gap) show a similar composition. Both countries have 36 recorded 

 species of which 22 species are common to both countries. The relation of these 

 countries to the Congo Basin zone is similar, Ghana sharing 24 species while Nigeria 

 has 28 species in common with the Congo Basin. Further west in Sierra Leone, of 

 the 26 species occurring there, 19 are species occurring in the Congo Basin zone. The 

 number of species common to both sides of the Dahomey rain-forest gap suggests 

 that the gap has had no effect on the species composition on either side of it. Either 

 when the gap was formed from the continuous block of western rain-forest, the 

 species were fairly evenly distributed or the spread of the species across the gap was 

 not impeded. It is impossible to obtain direct evidence of the direction of spread 

 of the fauna but from the present study it is suggested that this spread was from the 

 Congo Basin into the West African zone. Considering the West African zone as 

 consisting of the countries given on p. 20, comparisons can be made of the species 

 in common between this zone and the others. Out of a total of 61 species, 52 of 

 these also occur in the Congo Basin. Similarly the zone has 31 species in common 

 with the East African zone and 26 species in common with the Southern African 

 zone. With the poorly collected North East African zone, 9 species are common to 

 this and the West African zone. 



Congo Basin Zone 



This zone is richest in the total number of species (88) but in the countries within 

 the zones the differences in the sizes of collections available is apparent. The 

 Central African Republic has only 8 species while the Cameroon has 46 species. The 

 number of apparent endemics is larger than the West African zone but the total 

 fauna is bigger. However, the ratio of endemic to non-endemics is higher in the 

 Congo Basin than in West Africa (approximately 1 : 9 in the West; 1 : 6 in the 

 Congo, endemics: non-endemics). The Congo Basin zone has 45 species in common 

 with the East African zone. This large number is mainly influenced by species 

 which extend only to the west of Uganda from the Congo and this part of Uganda, as 

 in other groups (e. g. Moreau, 1966) should be regarded as part of the Congo Basin. 

 The Congo Basin has 31 species in common with the Southern African zone and this 



