114 MAXIJAL OP THE MOLLUSCA.. 



the clouds discliarge themselyes on tlie east side of tlie Andes, 

 and rain is so rare on tlie west coast that in some parts it only 

 falls two or three times in a century. In Peru, during great 

 part of the year, a vapour rises in the morning, called the 

 "garua; " it disappears soon after midday, and is followed by 

 hea\^ dews at night. 



Mr. Cuming collected 46 species of land snails in Peru ; and 

 Dr. Pfeiffer enumerates 100, but perhaps half the latter were 

 from the eastern side of the Andes, belonging to the Brazilian 

 Province. They are mostly Bulimi, and are smaller and less 

 richly coloured than those of Bolivia and Brazil ; B. Denichei, 

 solutus, and turritus are peculiar forms. Cistula Delatreana is 

 the only oiDerculated land snail, and Vaginulus limayanus the 

 only slug. 



Helix 12 Pupa 1 Ancjius 1 



Bulimus 79 Balea 1 AmpuUaria 1 



Succinea 5 Cistula 1 Paludestrina 2 



Griandina 1 Physa 1 CjTena 3 



Tornatellina 1 Planorbis 3 Anodon 1 



25. Argextust: Eegion. 



The '' region of arborescent Compositae" has afforded scarcely 

 any land snails ; only 7 species of BuUmus, and 3 Helices are 

 recorded, but some others may have been included with those 

 of Brazil and Cliili. From Boli-vda this province is separated 

 by the wide plains of the Great Desert, or northern prolonga- 

 tion of the Pampas ; and all the eastern part has been submerged 

 at a recent (geological) period; so that the only promising 

 districts are Paraguay and the eastern declivities of the Chilian 

 Andes. The fi^esh-water shells of the La Plata and its tribu- 

 taries are more remarkable. 



Chilinia 7 Cyclas 1 Byssoanodon 1 



Planorbis 11 Pisidium 1 Monocondylsea 6 



Ancylus 4 Corbiciila 2 Mj'cetopus 1 



AmpuUaria 7 Unio 7 Castalia 1 



Asolene 1 Anodon 10 Iridina 1 



Paludestrina 7 



AmpuUaria (Marisa) cornu-arietis is a characteristic shell; 

 Paludestrina lapidum has a claw-like (non-spiral) operculum, 

 and appears to belong to the Melaniadce. 



26. Chilian Eegion. 



The northern part of Chili belongs to the same physical region 

 with Peru, consisting of dry and rainless plains. Here the land 



