206 FAUNA OF MASCARENE, COMORO, AND SEYCHELLE ISLANDS 



peculiar to this group of islands, where the typical snails (Helicidce) are but poorly 

 developed. 



In the Mascarenes proper the percentage of peculiar species of land and fresh- 

 water molluscs is very high, and is paralleled only in some of the West Indian 

 Islands. Some years ago it was recorded that of these peculiar species Mauritius 

 had one hundred and thirteen, Reunion forty-five, and Rodriguez twenty-three. 

 This seems indicative of long insulation ; but, apart from these peculiar types, the 

 molluscan fauna of the group exhibits Malagasy, Indian, and Australasian affinities. 

 The most abundant peculiar generic type of land-snail is Pachystyla, belonging to 

 the family Naninidce, and confined to the Mascarenes, exclusive of the Seychelles. 

 The most peculiar and characteristic type is, however, the carnivorous genus Gibbus, 

 so named from the irregular and humped form of the conical and big-mouthed 

 shell ; it is most abundant in Mauritius, and represented by the allied Edentulina 

 and Streptostele in the Seychelles. The presence of Cyclostoma, most of the 

 Mauritian species of which are extinct, affords the strongest evidence of the affinity 

 of the molluscan fauna of these islands with that of Madagascar. On the other 

 hand, some eleven genera, of all of which the names need not be particularised, 

 are indicative of relationship with the Indian and Australian regions, none of them 

 occurring in Madagascar. Most interesting of all is the presence of the genus 

 Hyalimax, elsewhere known only in the Andamans and Nicobars, and thus afford- 

 ing strong evidence of a former land connection between the Mascarenes and India 

 by way of these islands. 



