Inoperculate 362 221 152 75 Operculate 252 242 100 23 It appears, then, that the proportion of operculate to inoperculate species, while very high in Cuba (about 41 per cent of the whole), reaches its maximum in Jamaica (where the operculates are actually in a majority), begins to decline in San Domingo (about 40 per cent), and continues to do so in Porto Rico, where they are not more than 24 per cent of the whole. These operculates almost all belong to the families Cyclostomatidae and Helicinidae, only two genera (_Aperostoma_ and _Megalomastoma_) belonging to the _Cyclophorus_ group. Comparatively few genera are absolutely peculiar to the islands, one or two species of most of them occurring in Central or S. America, but of the several hundreds of operculate species which occur on the islands, not two score are common to the mainland. [Illustration: Map to illustrate the GEOGRAPHICAL DISTRIBUTION of the Land Mollusca of the WEST INDIES. _The red line marks the 100 fathom line._ London: Macmillan and C^ọ. _London: Stanford’s Geog^ḷ Estab^ṭ._] The next special feature of the sub-region is a remarkable development of peculiar sub-genera of _Helix_. In this respect the Antilles present a striking contrast to both Central and S. America, where the prime feature of the land Pulmonata is the profusion of _Bulimus_ and _Bulimulus_, and _Helix_ is relatively obscured. No less than 14 sub-genera of _Helix_, some of which contain species of almost unique beauty and size, are quite peculiar to the Greater Antilles, and some are peculiar to individual islands. Here, too, is the metropolis of _Cylindrella_ (of which there are 130 species in Cuba alone), a genus which just reaches S. America, and has a few species along the eastern sea-board of the Gulf of Mexico. _Macroceramus_ and _Strophia_ are quite peculiar; the former, a genus allied to _Cylindrella_, which attains its maximum in Cuba and San Domingo, is scarcely represented in Jamaica, and disappears south of Anguilla; the latter, a singular form, resembling a large _Pupa_ in shape, which also attains its maximum in Cuba, is entirely wanting in Jamaica, and has its last representative in S. Croix. One species irregularly occurs at Curaçao. The carnivorous group of land Mollusca are represented by several peculiar forms of _Glandina_, which attain their maximum in Jamaica and Cuba, but entirely disappear in the Lesser Antilles.