The land operculates belong principally to the families Cyclostomatidae and Helicinidae. Of the former, Cuba is the metropolis of Ctenopoma and Chondropoma, the former of which includes 30 Cuban species, as compared with 1 from San Domingo and 2 from Jamaica. Megalomastoma (Cyclophoridae) is also Haitian and Porto Rican, but not Jamaican. Blaesospira, Xenopoma, and Diplopoma are peculiar. The Helicinidae consist mainly of Helicina proper (58 sp.), which here attains by far its finest development in point of size and beauty, and of Eutrochatella (21 sp.), which is peculiar to the three great islands (Jamaica 6 sp., San Domingo 6 sp.).
The Bahamas, consisting in all of more than 700 islands, are very imperfectly known, but appear to be related partly to Cuba, partly to San Domingo, from each of which they are separated by a narrow channel of very deep water. They are certainly not rich in the characteristic groups of the Greater Antilles. The principal forms of Helix are Plagioptycha (6 sp.), common with San Domingo, and Hemitrochus (6 sp.), common with Cuba. Strophia is exceedingly abundant, but Cylindrella, Macroceramus, and Glandina have but few species. There are a few species of Ctenopoma, Chondropoma, and Cistula, while a single Schasicheila (absent from the rest of the sub-region) forms a link with Mexico.
Fig. 229.—Characteristic Cuban Helices. A, Polydontes imperator Montf. B, Caracolus rostrata Pfr. C, Polymita muscarum Lea.
Southern Florida, with one or two species each of Hemitrochus, Cylindrella, Macroceramus, Strophia, Ctenopoma, and Chondropoma, belongs to this province.
(b) Jamaica.—The land Mollusca of Jamaica are, in point of numbers and variety, quite unequalled in the world. There are in all as many as 56 genera and more than 440 species, the latter being nearly all peculiar. The principal features are the Glandinae, the Helicidae, and the land operculates. The Glandinae belong principally to the sub-genera Varicella, Melia, and Volutaxis, Streptostyla being absent, although occurring in Cuba and San Domingo. There are 10 genera of Helix, of which Pleurodonta is quite peculiar, while Sagda (13 sp.) is common only with S.W. San Domingo (2 sp.), and Leptoloma (8 sp.) only with Cuba (1 sp.). The single Strobila seems to be a straggler from a N. American source. Macroceramus has only 2 species as against 34 in Cuba, and of Cylindrella, in which Cuba (130 sp.) is so rich, only 36 species occur. The genus Leia, however (14 sp.), is all but peculiar, occurring elsewhere only in the neighbouring angle of San Domingo, which is so closely allied with Jamaica. The complete absence of Strophia is remarkable.
Fig. 230.—Characteristic Jamaican and Haitian Mollusca: A, Sagdae pistylium Müll., Jamaica; B, Chondropoma salleanum Pfr., San Domingo; C, Eutrochatella Tankervillei Gray, Jamaica; D, Cylindrella agnesiana C. B. Ad., Jamaica.
The land operculates form the bulk of the land fauna, there being actually 242 species, as against 221 of land Pulmonata, a proportion never again approached in any part of the world. As many as 80 of these belong to the curious little genus Stoastoma, which is all but peculiar to the island, one species having been found in San Domingo, and one in Porto Rico. Geomelania and Chittya, two singular inland forms akin to Truncatella, are quite peculiar. Alcadia reaches its maximum of 14 species, as against 4 species in San Domingo and 9 species in Cuba, and Lucidella is common to San Domingo only; but, if Stoastoma be omitted, the Helicinidae generally are not represented by so many or by so striking forms as in Cuba, which has 90 species, as against Jamaica 44, and San Domingo 35.
(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.