The Cylindrellidae find their maximum development in Cuba. As many as 34 _Macroceramus_ occur (two-thirds of the known species), and 130 _Cylindrella_, some of the latter being most remarkable in form (see Fig. 151, B, p. 247). 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. [Illustration: 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.