XI THE NEOTROPICAL REGION 343 



Isomeria, Solaroiisis) 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 c[uarter of 

 the world, particularly in the genera Glandina and Streptostyla. 

 These genera also penetrate the northern portions of the con- 

 tinent, Glandina reaching as far as Ecuador, and Streptostyla as 

 far as Peru. The Greater Antilles have also characteristic forms 

 of these genera. Stre{ptao:is is tolerahly 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. VaginvJa occurs through- 

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



CI a us il la, 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 prol:)al3ility 



made its way into S. America in 



exceedingly remote ages from its head- ^" * ' 



quarters in Eastern Asia. No species 



survives in N. America, and a single 



strao-o-ler is found in Porto Eico. The ^^ .^o .. , . r,. 



'^^ /" 7- 77 1 FrG.z28. — HomalonyximguisY&w, 



genera Macroceramus, CyiindreUa, and Demerara. sh, Shell (siiowu 



Strophia, are characteristic West also separate); i^.c, imlmonary 



Indian forms, which are only slightly 



represented on the mainland. Homalonyx, a curious form akin 



to Succinea, 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 ]\Iolluscan fauna. Several groups of the 

 Cyclostomatidae find their headquarters here, and some spread 

 no farther. On the mainland this prominence does not continue. 

 AVest 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 disappears in 

 Chili and Argentina, becomino; scarce even in Brazil. 



Among the fresh-water operculates, Amjndlaria is abundant, 

 and widely distributed. Vivipara, so characteristic of N. 

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

 pulmonate, akin t(j Limnaca, is peculiar to Cliili, Patagonia, and 



