XI THE NEOTROPICAL REGION 343 



Isomeria, Solaropsis) occur, which disappear altogether towards 

 the south. 



Carnivorous land Mollusca are, so far as Central America is 

 concerned, more highly developed than in any other quarter of 

 the world, particularly in the genera Glandina and Streptostyla, 

 These genera also penetrate the northern portions of the con- 

 tinent, G-landiiia reaching as far as Ecuador, and Streptostyla 

 as far as Peru. The Greater Antilles have also characteristic 

 forms of these genera. Streptaxis is tolerably abundant all over 

 tropical South America, and is the one pulmonate genus which 

 shows any affinity with the African fauna. 



The slugs are exceedingly scarce. Vaginula occurs through- 

 out, and is the only genus in any sense characteristic. 



Clausilia^ in the sub-genus Nenia^ occurs along the Andean 

 chain from the extreme north (but 

 not in Central America) as far south 

 as Bolivia. It has in all probability 

 made its way into S. America in ex- 

 ceedingly remote ages from its head- 

 quarters in Eastern Asia. No species 

 survives in N. America, and a single 

 straggler is found in Porto Rico. The 



71*- n T 1 n 1 Fig. 228. — Homalonyx unauis 



genera Macroceramus, Cylindrella, and ^^^^^ Demerara. sh, Shell 

 StrovJiia^ are characteristic West Ind- (shown also separate); p.o, 



r. 1 • 1 1 T 1 i 1 pulmonary orifice. 



lan forms, which are only slightly re- 

 presented on the mainland. Homalonyx^ a curious form akin to 

 jSuccinea, is peculiar to the region. 



Land operculates attain a most extraordinary development 

 in the Greater Antilles, and constitute, in some cases, nearly 

 one-half of the whole Molluscan fauna. Several groups of the 

 Cyclostomatidae find their headquarters here, and some spread 

 no farther. On the mainland this prominence does not con- 

 tinue. West Indian influence is felt in Central America and 

 on the northern coast district, and some Antillean genera make 

 their way as far as Ecuador. The whole group entirely disap- 

 pears in Chili and Argentina, becoming scarce even in Brazil. 



Among the fresh-water operculates, Ampullaria is abun- 

 dant, and widely distributed. Vivipara^ so characteristic of N. 

 America, is entirely absent. Chilina, a remarkable fresh-water 

 pulmonate, akin to Limnaea, is peculiar to Chili, Patagonia, and 



