HYPSOMETRICAL OlSTRUJI TION, ETO. 207 



niollusks are very numerous, the lluviatiie genera being- entirely 

 confined Avithin this limit. 



2. From 3000 to 4500 feet. This is the greatest height attained 

 by a number of species of Helix, Hyalina, Yitrina, Pupa, Clan- 

 silia, etc.; some of which are found also in the lower valleys. 



3. From 4500 to 6000 feet. Fischer has called this the zone 

 of Helix memoralis^ which occurs no higher, and which is found 

 on rocks and wooded heights. In the Alps the same mollusks 

 occur at a greater altitude than in the Pyrenees and Auvergne : 

 thus Helix arbustoruvi^ Iiispida, Hyalina diaphana, Gionella 

 lubrica^ having their upper limit within this zone in the Alps, in 

 the other regions do not attain be3^ond 3000 to 4500 feet. 



4. From 6000 to 8000 feet. The number of mollusks is much 

 reduced, the species decidedly Alpine in character. The relation 

 between the distribution of terrestrial mollusca and that of the 

 plants on which they feed, is of course very intimate ; thus in 

 the Higher Kab^dia, Aucapitaine's observations have resulted 

 in establishing three zones of distribution for niollusks, namely : 



1, that of the ashes, olives and pomegranates (450 to 2100 feet) ; 



2, that of the oaks and pines (2100 to 3600 feet) : 3, that of the 

 cedars and green turf (3600 to 1200 feet). At Guadeloupe, 

 West Indies, Succivea Sagi^a and Hovialonyx unguis are found 

 on the lowest lands ; Stenogyra octona, Leptinaria lamellata^ 

 Opeas Garaccasensis occur no higher than 250 to 300 feet ; 

 Bulimus exilis, 600 feet ; Helix lychnuchus, dentiens, Josephinae, 

 pacliygastra.1 occur in forests at 900 to 1200 feet ; Pellicula 

 appendiculata lives in the region of palms, between 1800 and 

 2100 feet ; Bulimus limnoides and chrysalis are abundant between 

 2000 and 2500 feet among roots ; finally Bulimulns Lherminieri 

 exceeds 2500 feet. 



Arthur Morelet has established five molluscous zones for Peru 

 and Bolivia, as follows : 1, Maritime Region, up to 2000 feet; 

 2, Region of the Montana, from 2000 to 5000 feet ; 3, Temperate 

 Region, from 5000 to 8000 feet ; 4, Cold Region, from 8000 to 

 12,000 feet; 5, Icy Region, from 12,000 to 16,000 feet. Within 

 this latter region occur the following : Limax Andecolus, Bulimus 

 culmineus^ B. nivalis^ B. ochraceus, B. Yanamensis, B. Weddelli, 

 Pupa Paradesi, Planorhis montaniis, P. Andecolus, Paludesirina 

 Andecola, P. culminea, Cyclas Fo7-be.si. The fluviatile mollusks 

 enumerated occur iu Lake Titicaca, the altitude of which is 

 nearly 13,000 feet. 



Mexico maj^'be divided into three zones: 1, Tropical, up to 

 2500 feet; 2, Temperate, 2500 to 5000 or 6000 feet; 3, Cold. 

 Among the species of the cold zone are : Bulimulus Ghieshreghti, 

 B. sulcosus, Helix Humboldtiana, Glandina coronata, G. Grizabee, 

 Planorbis tenuis^ Limnsea attenuata. The two latter inhabit the 

 Lake of Mexico, at over 1000 feet altitude. 



