13? COOKE: GEOGRAPHICAL DISTRIBUTION OF MOLLUSCA. 



The special characteristics of the region are the great develop- 

 ment of the carnivorous land mollusca (Ennea, Gilwts), the 

 occurrence of a considerable number of true Helicidiz of great size 

 and beauty, and the prominence of the genus Cyclostoma. In the 

 two latter of these points, the region stands in complete and 

 pronounced contrast to the whole of the Ethiopic province. The 

 points of individuality will be better brought out by a survey of the 

 separate islands, since in several cases their fauna exhibits 

 considerable divergence. 



(a) The Madagascan Sub-region. — The land mollusca of the 

 great island of Madagascar, although as yet imperfectly known, 

 possess a striking individuality, and, even if considered quite apart from 

 its other zoological features, would be quite sufficient to separate it 

 off, in a decisive manner, from the mainland of Africa. Two of the 

 chief characteristics of the Ethiopic province are the paucity of its 

 operculate and of its Helix fauna ; Madagascar is especially 

 distinguished by the rich development of both these groups. For 

 size, colouring, and beauty of shape, the Helicidcc in the two 

 subgenera Ampelita and Helicophanta^ rival, if they do not surpass, 

 any in the world. They are quite peculiar to this sub-region, not 

 a trace of them occurring on the Mascarenes, Seychelles, or even on 

 the Comoros. Their nearest relationships appear to be with the 

 Acavi of Ceylon and the great Panda of N.E. Australia. As is 

 usual when Helix is well developed, the Zonitidce {JVaninid(c) are 

 proportionately few, not more than a dozen being known to occur. 

 The peculiar feature of the operculate fauna is the exceedingly rich 

 development of Cyclostoma proper (54 sp.), of which Madagascar 

 may be regarded as the metropolis. Many of the species are of 

 great size and of striking beauty of ornamentation. Unlike 

 its Helicid(B % this genus is not restricted to Madagascar ; several 

 species occur on the mainland, six on the Comoros, one on the 

 Seychelles, and 12 in Mauritius and Bourbon. The subgenera 

 Acroptychia and Hainesia are peculiar. There is nothing remarkable 

 about the rest of the operculate fauna, Lilhidion, Otopoma and 

 Cycloplwrus all being represented on the mainland. Omphalotropis, 

 so abundant on the Mascarenes, does not occur. 



The African Bulimini {Pachnodus and Rachis) are each repre- 

 sented by two species, but Achatina, so abundant on the mainland, 

 is comparatively scarce. Two other groups of Buliminus, 

 Leucotcefiia and Clavator, are quite peculiar. The presence of a 

 single Kaliella, specifically identical with a common Indian form, is 

 very remarkable. 



