(_c_) _San Domingo_, although not characterised by the extraordinary richness of Cuba and Jamaica, possesses many specially remarkable forms of land Mollusca, to which a thorough exploration, when circumstances permit, will no doubt make important additions. From its geographical position, impinging as it does on all the islands of the Greater Antilles, it would be expected that the fauna of San Domingo would not exhibit equal signs of isolation, but would appear to be influenced by them severally. This is exactly what occurs, and San Domingo is consequently, although very rich in peculiar species, not equally so in peculiar genera. The south-west district shows distinct relations with Jamaica, the Jamaican genera _Leia_, _Stoastoma_, _Lucidella_, and the _Thaumasia_ section of _Cylindrella_ occurring here only. The north and north-west districts are related to Cuba, while the central district, consisting of the long band of mountainous country which traverses the island, contains the more characteristic Haitian forms. The Helicidae are the most noteworthy of the San Domingo land Mollusca. The group _Eurycratera_, which contains some of the finest existing land snails, is quite peculiar, while _Parthena_, _Cepolis_, _Plagioptycha_, and _Caracolus_ here reach their maximum. The Cylindrellidae are very abundant, but no section is peculiar. Land operculates do not bear quite the same proportion to the Pulmonata as in Cuba and Jamaica, but they are well represented (100 to 152); _Rolleia_ is the only peculiar genus. The relations of San Domingo to the neighbouring islands are considerably obscured by the fact that they are well known, while San Domingo is comparatively little explored. To this may perhaps be due the curious fact that there are actually more species common to Cuba and Porto Rico (26) than to Porto Rico and San Domingo. Cuba shares with San Domingo its small-sized _Caracolus_ and also _Liguus_, but the great _Eurycratera_, _Parthena_, and _Plagioptycha_ are wholly wanting in Cuba. The land operculates are partly related to Cuba, partly to Jamaica, thus _Choanopoma_, _Ctenopoma_, _Cistula_, _Tudora_, and many others, are represented on all these islands, while the Jamaican _Stoastoma_ occurs on San Domingo and Porto Rico, but not on Cuba, and _Lucidella_ is common to San Domingo and Jamaica alone. An especial link between Jamaica and San Domingo is the occurrence in the south-west district of the latter island of _Sagda_ (2 sp.). The relative numbers of the genera _Strophia_, _Macroceramus_, and _Helicina_, as given below (p. 351), are of interest in this connexion.