’ @ 
1927] Pilsbry-Bequeart, The Aquatic Mollusks of the Belgian Congo 095 
modified from the ancestral type, so that it seems to us Meaningless to 
look for their ancestors among Mesozoic fluviatile snails similar in appear- 
ance to some of the present day Tanganyikans.! To speculate further 
upon the history of the Tanganyikan mollusks would hardly serve a 
useful purpose, since we know nothing whatsoever of the fluviatile forms 
that lived in Central Africa during the Mesozoic and early Cenozoic. 
Lake Moero 
Lake Moero (or Mweru) extends over an area of about 4,850 square 
kilometers, between 8° 30’ and 9° 30’S., 28° 30’ and 29° E., being about 
120 kilometers long from northeast to southwest and nearly everywhere 
some 40 kilometers wide.? In the west it is bordered by the steep, moun- 
tainous slopes of the Kundelungu Plateau, rapidly rising to 1,400 m. 
above sea level. Here the shore often forms cliffs and presents no harbors 
nor bays, while the few small affluents come down in cascades. The 
northern shore is rather gentle, with occasional, narrow, sandy beaches; 
it receives two affluents of moderate size, the Lunkinda and the Loao. 
The Luvua (usually called Lualaba by the natives), the outlet of the lake, 
flows out of the extreme northwestern corner. The east coast is also 
bordered by cliffs, but they are much lower than on the western shore, 
and the ascent to the highland is more gradual. An important eastern 
affluent, the Kalungwesi, drains a large portion of Northeast Rhodesia. 
The southern shore is very low, frequently marshy or covered with 
rushes or papyrus swamps, and continuesinland as a slightly raised, uni- 
formly flat, alluvial plain, almost as large as Lake Moero itself. This 
plain is still partly flooded at the height of the rainy season. Topographic 
conditions show that it has only recently emerged above the waters and 
the shrinking process of the lake appears to be steadily continuing now- 
adays. The Luapula, carrying the waters of Bangweolo, enters at the 
southern end through a small, swampy peninsula which projects into the 
lake. West of the mouth of the Luapula there is a deep bay which receives 
1C, A. White and L. Tausch. have called attention to the superficial resemblance between certain 
thalassoid gastropods of Tanganyika and some lacustrine Upper Cretaceous or HKocene fossils; especially 
between Pyrgulifera and Paramelania, and between Fascinella and Syrnolopsis. They assume that 
this similarity is sufficient proof of a direct relationship between the forms in question. There is no 
way of proving that in cae cases the resemblance is not as fortuitous as is the external likeness with 
tain Jurassic marine snails. 
ih White, C. A. 1881. ‘Tanganyika shells.’ Nature, XXV, pp. 101-102. ; 
1882. ‘New molluscan forms from the Laramie and Green River group, with discussion of some 
associated forms heretofore known.’ Proc. U.S. Nat. Mus., V, pp. 94-99, Pls. 11-1v (see p. 98). 
Tausch, L. 1884. ‘Ueber einige Conchylien aus dem Tanganyika See und deren fossile Ver- 
wandte.’ Sitz. Ber. Ak. Wiss. Wien, Math. Naturw. K]., XC, Abt. 1, pp. 56-70, Pls. 1-11. ; 
Oppenheim, P. 1892. ‘Ueber einige Brackwasser- und Binnenmollusken aus der Kreide und dem 
Eocin Ungiarns.’ Zeitschr. Deutsch. Geol. Ges., XLIV, pp. 697-818, Pls. xxx1—xxxv1 (see pp. 750-752). . 
2The altitude of Lake Moero is variously given as 912 m., 936.m., or 972 m. above. 
