562 Bulletin American Museum of Natural History [Vol. LIII 
It may be seen that the fauna is still typically fluviatile, even though 
the water has a slight brackish taste. The species of Lanzstes live mainly 
. inthe papyrus swamps. Melanoides crawls in the usual fashion over the 
immersed sand spits,.in which are also buried the various Unionide and 
the Mutela, most of them in great abundance. The strikingly winged, 
large Neritina frequents deeper stretches of water with rather steady 
current, where it is attached to stones or to submerged dead branches. 
In traveling downstream from Zambi toward Malela a decided 
change of conditions is noticed upon reaching the western extremity of 
Mateba Island. The river is then more fully exposed to the effect of the 
tides and the water becomes extremely brackish, at least at the flood. 
Malela is well within this brackish zone, an area of muddy tidal flats 
covered with halophytic vegetation, primarily with true mangrove-forest 
(Rhizophora Mangle Linnzeus) and divided into numerous islands by 
tortuous and deep creeks. Although composed of but a few species of 
plants, the vegetation of these muddy islands, periodically covered and 
uncovered by the tide, is quite luxuriant. Rhizophora Mangle, the com- 
mon mangrove tree of the shores of the Atlantic Ocean, reaches here much 
larger dimensions than anywhere else in the world. Along the creeks 
between Malela and Banana it forms dense stands, 25 to 30 m. high, 
with columnar boles frequently 60 cm. in diameter. As shown in PI. 
LXXIV,from a photograph taken near,Malela at low tide, these hugetrunks 
are solidly anchored in the oozy bottom by a system of short, spreading 
prop roots. On the outer edges of such tall timber Rhizophora also sends 
down from the branches high up in the canopy long, dichotomous roots, 
which merely dangle loose in the water. These characteristics may be 
seen from Pl. LX XIII, which also illustrates the dense fringe of low 
Raphia palms, another peculiarity of the area immediately below Malela. 
The vicinity of Malela possesses a rather varied and extremely inter- 
esting assemblage of mollusks, as may be seen from the following list: 
Neritina owentana Pachymelania fusca 
Lanistes congicus (?) Egeria congica 
" AnLortus ‘*  tenwuicula langt 
Potamides fuscatus Me Petar 
Melanordes langi Iphigema congo 
Cexlatura elegans 
But few truly marine species reach so far up river, the most common 
being a species of Teredo which bores into the piles of the wharf. On the 
muddy shores of the Congo estuary a species of Corbula also occurs in 
abundance together with Iphigenia. The most prominent members of 
