XI ANTILLEAN SUB-REGION 345 



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 Bulimidus., 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 indi- 

 vidual 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. Macroceramiis and Stropliia are quite peculiar; the 

 former, a genus allied to Ct/linchella, 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 maxi- 

 mum in Cuba, is entirely wanting in Jamaica, and has its last 

 representative in S. Croix. One species irregularly occurs at 

 Cura9ao. 



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. 



A certain number of the characteristic N. American genera 

 are found in the Antillean Sub-region, indicating a former con- 

 nexion, more or less intimate, between the W. Indies and the 

 mainland. The genera are all of small size. The characteristic 

 N. American Hyalinia are represented in Cuba, San Domingo, 

 and Porto Rico; among the Helicidae, Polygyra reaches Cuba, 

 but no farther, and Strohila Jamaica. The fresh-water Pulmo- 

 nata are of a X. American type, as far as the Greater Antilles 

 are concerned, but the occurrence of Grimdlachia (Tasmania and 

 Trinidad only) in Cuba is an unexplained problem at present. 

 Unionidae significantly occur only at the two ends of the chain 

 of islands, not reaching farther than Cuba (TJnio 3 sp.) at one 

 end, and Trinidad (which is S. American) at the other. 



A small amount of S. American influence is perceptible 

 throughout the Antilles, chiefly in the occurrence of a few species 

 of Bidimulus and Simpulopsis. The S. American element may 



