358 ARGENTINA — CHILI chap. 



phia are common with the Colombian Sub-region, and Oxychona 



(4 sp.) with the Central American. Bidimus 

 has in all 36 species, the sub-genera Pachyo- 

 tus (Fig. 233) and Strophochilus being pecul- 

 iar. Bulimulus^ though not so abundant as 

 in Peru and Ecuador, has about 60 species, of 



Fig. 235. — Buiimuius which Navicula (Fig. 235) is the most remark- 



m7n!''BlzT''''^'' able group. Megaspira is peculiar. Ortliali- 



cus has only 4 species, while Tomigerus (4 sp.) 



and Anostoma (3 sp.) are common with Venezuela. Land opercu- 



lates are scarce, and appear to include only Neocyclotus^ Oyclo- 



phorus^ and Helicina. 



In Argentina, which may probably rank as a separate pro- 

 vince, the tropical forms greatly decrease, 



Streptaxis being reduced to 2 species, and 



Bulimus and Buiimuius together to 40, while 



Orthalicus^ the great Helices, and the land 



operculates disappear altogether. Odonto- 



stomus (Fig. 236), a genus of the Pupidae, is 



abundant in the northern part of the province. 



Two or three species of Chilina occur. 



(5) The Chilian Sub-region. —The greater ^^^ 2m. - Odonto- 



part of Chili, from its arid and rainless climate, stomus pantagru- 



is unfavourable to the existence of land Mol- eimus Monc, s. 



Brazil, xi. 



lusca. Bulimus (^Borus) still has 3 or 4 species, 

 and Bulimidus (^Ple do stylus 11, Scutalus 9, Peronaeus 7) is 

 fairly abundant, but the profusion of the tropics is wanting. 

 There are no carnivorous genera, and only two land operculates. 

 A remarkable form of Helix (^Macrocyclis^ Fig. 237) is quite 

 peculiar, but the majority of the species belong to two rather 

 obscure groups, Stepsanoda and Amphidoxa. Chilina^ a singu- 

 larly solid form of Limnaea (of which 8 sp., with a sub-genus 

 Pseudochilina^ occur in Chili), is peculiar to Chili, S. Brazil, 

 and Patagonia. From the two islands of Juaii Fernandez and 

 Masafuera^ are known several Helix^ of Chilian affinity, several 

 curious Succinea^ a Homalonyx^ Leptinaria^ and Nothus^ and three 

 species of Tornatellina^ with the almost universal Limax gagates. 

 The question of the existence at some remote period of a 

 Neantarctic continent, which formed a communication between 

 the three great southern peninsulas of the world, is one on 



