CHAPTER XI 



(IKOGRAPHICAL DISTRIBUTION OF LAND MOLLUSCA (continued') 

 — THE ETHIOPIAN, NEARCTIC, AND NEOTROPICAL REGIONS 



D. The Ethiopian Region 



The Etliioj^ian region includes the whole of Africa south of 

 the Great Desert, and Southern Arabia, together with the outly- 

 ing islands, excepting those of the Atlantidean province (p. 297). 



Regarded as a whole, the Ethiopian is poorest in land Mollusca 

 of all the tropical regions. And yet its characteristics are very 

 remarkable. The entire Achatina group is peculiar, and takes, 

 especially in W. Africa, some curious forms (Columna, Perideris^ 

 Pseudachatina). Carnivorous Mollusca (Ennea^ Gihhus^ etc.) 

 are highly developed, especially in the south and east, the largest 

 known helicoid form (Aerope) being from Natal. In the posses- 

 sion of these types of the Agnatha, Africa is more closely related 

 to the Australasian than to the Oriental region. The true Cyclo- 

 stoma are entirely peculiar to the region, but are absent from 

 West Africa. 



Fresh-water Mollusca are abundant and characteristic, espe- 

 cially in and near the Great Lakes. Lanistes, Cleopatra,, and 

 Meladomus, among the operculates, together with Mutela and 

 Aetheria (Unionidae), G-alatea and Fischer ia (Cyrenidae), are 

 peculiar. 



In its negative, as well as its positive features, the Ethiopian 

 region is markedly isolated. Helicidae and Naninidae are equally 

 deficient, the former, indeed, attaining some numerical predomi- 

 nance in the extreme south, but the species are nearly all insig- 

 nificant in size and colouring. It is only in ^ladagascar that 

 Helix asserts itself. Arion,) Limax^ Hyalinia^ Clausilia,, and a 



328 



