p00 Bulletin American Museum of Natural History — [Vol. LIII 
bottom of fine gravel and are but little obstructed by water-plants. Thus 
far, these waters have been but little investigated malacologically, 
although they may possess some forms of great interest. In Upper 
Katanga they have yielded a number of species not known elsewhere 
within our territory, as may be seen from the subjoined list. 
Lymnexa natalensis Lanistes nsendweensis katanganus 
Planorbis adowensis  eipacus 
é costilaius | Bulimus kisalensis 
Segmentina kempr Lobogenes michaelis 
Physopsis africana globosa s spiralis 
Burnupia caffra Melanoides anomala 
oe alta Cleopatra dautzenbergr 
& transvaalensis a nsendweensis 
S kimiloloensis Se a katangana 
Lanistes nsendweensis Pisidium katangense 
Unionide and Mutelide are generally absent from these smaller 
streams. Planorbis costulatus, Segmentina kempi, Lanistes ellapticus, 
Bulimus kisalensis, Lobogenes michaelis, L. spiralis, Melanoides anomala, 
and Pisidium katangense are an interesting assemblage from the clear 
water of streamlets near Elisabethville, the smaller species actually 
living partly buried in the fine pebbles of gravelly bottoms, near the 
sources, as noted by their discoverer, Dr. Michael Bequaert. 
Sometimes these headwaters are interrupted by falls or rapids, such 
as those shown for the Lubumbashi River near Elisabethville on Pl. LXTX, 
fig. 2. Ecological conditions are then more like those of the cataracts 
of larger rivers, of which we shall have more to say later. 
In the hilly portions of the Ituri forest there are many shallow 
brooks, gently meandering beneath the dense shade of the trees, except 
when a freshet transforms them into temporary torrents. These forest 
streams differ mainly from the brooks of the savanna country in that 
they nourish much plant growth and also contain abundant decaying 
vegetable matter. As seen in the photograph of Plate LXV, taken near 
Niapu, the partly immersed boulders and dead tree stumps of the bed 
and of the banks are covered with many hygrophilous plants, such as 
liverworts, mosses, selanigellas, club-mosses, ferns, sedges, etc. Among 
the dead leaves and decaying branches of the bottom one should look for 
the species of Potadoma, usually partly buried in the débris and heavily 
coated with hydroxid of iron and dirt. They are apparently the only 
mollusks to be found in this particular habitat, where they occur with 
river crabs of the genus Potamon. Since they present a number of species 
