498 BulletinAmerican Museum of Natural History [Vol. LIII 
the coldest (August), 23° .69 C. In the maritime region and throughout 
the Lower Congo the vicinity of the sea results in a considerable humidity 
of the atmosphere during the dry season, so that the sky is usually 
clouded and fogs are not uncommon in the early morning. Consequently, 
the influence of the drought on plant and animal life is much less marked 
than farther east in the Kasai basin and Lower Katanga. 
The vegetation (Pl. LIV, fig. 2) is of the same general type as in 
the Ubangi Savanna District. The maritime zone, to a distance of about 
80 kilometers from the shore of the Atlantic, is a low, level plateau 
mostly covered with high-grass savanna, occasionally with scattered 
boabab trees and, on the alluvial plains and islands of the Congo estuary, 
also with interspersed palms (Hyphene guineensis Schumacher and 
Thonning).! The Crystal Mountains are a region of much greater barren- 
ness, owing to the rocky nature of much of the surface soil. The hillsides 
are usually covered with a rather depauperate grass vegetation, with 
sparse and stunted scrubs. The many torrential streams, however, run 
in gulleys narrowly fringed with small trees; while more extensive 
patches of forest are met with along the alluvial banks of the larger rivers, 
such as the Inkisi, and along the slopes of.certain mountain ranges (as on 
Mt. Bangu). Farther east, in the Kasai basin, the Manyema, and Lower 
Katanga, woody vegetation is more abundantly scattered in the grass 
and in many places the country has the aspect of a tree- or forest-savanna, 
and is sometimes park-like. Here, too, forest galleries are met with 
along all rivers and, on the lower Sankuru and mid-Kasai, they become 
very extensive, harboring there most of the forest animals and plants of 
the central Congo basin. : 
The malacological fauna of the Southern Congo Savanna is probably 
less known than that of any other part of our territory. In the large 
area of the Kasai basin, Manyema, and Lower Katanga collecting has 
been done in not more than a dozen localities, and in each of them but 
very few species have been obtained, so that a more detailed discussion 
does not appear worth while. The Lower Congo, however, is somewhat 
better known. | : 
In June, 1915, Mr. H. Lang and the junior author found a rather 
rich molluscan fauna estivating-in large numbers in the ravines of cal- 
careous sandstone hills which at Zambi form the banks of the Congo 
River. The torrents during the rainy season had washed the soil from 
the limestone slabs, which we moved one by one. Empty shells were 
'The peculiar mangrove vegetation on the tidal flats will be considered in connection with the 
brackish water mollusks of the mouth of the Con - \ 
