XI SAN DOMINGO 349 



(c) San Domingo^ althougli not characterised by the extraor- 

 dinary richness of Cuba and Jamaica, possesses many specially 

 remarkable forms of land Mollusca, to which a thorough explora- 

 tion, 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 char- 

 acteristic 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 Par- 

 thena^ CepoUs, Plagioptyclia^ and Caracolus here reach their 

 maximum. The Cylindrellidae are very abundant, but no sec- 

 tion 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 CaracoZws and also Liguus^ but the great Euryaratera^ Par- 

 thena^ and Plagioptycha are wholly wanting in Cuba. The land 

 operculates are partly related to Cuba, partly to Jamaica, thus 

 Clioanopoma., 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 



