§12 Bulletin American Museum of Natural History [Vol. LIT 
tion. Cattle, sheep, and goats are raised in considerable numbers, so 
that the combined efforts of man and beast have transformed most of the 
lower regions of this area, between 1,500 m. and 1,800 m., into a pasture 
land of short mountain grass almost bare of woody vegetation and ex- 
tremely poor in mollusks. In fact the only known species is Burtoa 
nilotica emint, which the junior author found crawling about in the short- 
grass prairie at Boswenda (1,800 m. above sea-level), near the foot of 
Mt. Mikeno.! There is every reason to believe that, ason Mt. Ruwenzori, 
mountain rain forest originally covered most of the Kivu country; but 
it is nowadays preserved only above 1,800 m., namely in what is 
known as the Bugoie and Rugege forests and on the several volcanoes of 
Mfumbiro. In the highlands of the western scarp of the Albertine Rift 
conditions are, however, more favorable for the preservation of woody 
vegetation. Mountain forest (Pl. LX, fig. 1), often mixed with bamboo 
thickets (Pl. LX, fig. 2), here forms a north to south strip 80 to 100 kilo- 
meters wide, which is continuous at its western edge with the Guinean 
rain forest of the Congo lowlands. When one travels from Rutshuru 
westward to the Lualaba the passage from the mountain forest to the 
Guinean rain forest occurs about midway between Masisi and Lubutu, 
near the crossing. of the Oso River, where the change in the nature of 
vegetation and fauna is extremely rapid and sharp. 
The malacological fauna of the Kivu Mountain Forest, between 
1,800 m. and 2,000 m., is extremely varied and very similar to that of the 
corresponding altitudinal life zone of Ruwenzori. This is well brought 
out by the following list of species obtained in the region of Masisi by the 
junior author (M) and on the island of Kwidjwi by Schubotz (K): 
Halolimnohelix mukuluensis M Pseudoglessula intermedia K 
bulla M ry = masisiensts M 
Achatina osbornt M A elatior K 
grauert M Curvella bathytoma M 
LInmicolaria saturata K “+ dautzenbergi M 
ie Fs masisiensis M Marconia kivuensis M 
7 elegans M, K ? lata ruwenzoriensis M 
Y pura K a latula M 
Homorus kwidschwiensis K Gonaxis micans M 
4 s nigricans M “  vulcani M 
Nothapalus sororcula M Streptostele streptosteloides K 
Subuliniscus lucast M 
_ Schubotz also obtained Burtoa nilotica at the foot of Mt. Muhavura and in Wau Island, Lake Kivu. 
His specimens were merely referred by \Thiele to the species, but it appears probable that they belonged 
to the subspecies emini. be 
