578 Bulletin American Museum of Natural History [Vol. LIII 
The other mollusks reported from Lake Edward appear to us of 
very doubtful occurrence there: Pala stuhlmanni, Bulamus humerosus, 
Melanoides tuberculata var. dautzenbergi, Sphxrium stuhlmanni, Aspa- 
tharia innesi, and Mutela nilotica. 
Practically all the species at present known from the lake were 
obtained in the shallow, southern part, where most of them are found in 
abundance, notably near the mouth of the Rutshuru River. The fauna 
of the deeper waters still remains to be investigated. ‘The mollusks are 
generally of small size. Although ten out of the nineteen forms are 
endemic, the malacological fauna is not very distinctive, since even the 
peculiar species are rather closely related to common Nilotic or even 
more generally distributed Ethiopian forms. Only some of the Planorbis 
appear to be of a distinct type (P. apertus, P. choanomphalus, and 
especially P. smithz), the shell being often more heavy than usual. It 
may be of someinterest that P. choanomphalus has been found elsewhere 
only in Lakes Victoria and Kivu. To the truly aquatic fauna of the lake 
should perhaps be added Succinea bequaerti, which lives at the southern 
shore in the thickets of rushes and reeds, fixed to these plants a short 
distance above the surface of the water. | 
Topographic and soil conditions of the surrounding territory clearly 
point to a former much larger extension of Lake Edward. Not so long 
ago, probably within historic times, it covered the low, alluvial, and 
more or less swampy plain to the northeast now partly occupied by Lake 
George and that near the mouth of the Rutshuru. Stuhlmann first 
reported the existence near Vichumbi, in the plain at the southern shore, 
of blackish alluviums containing an abundant shell fauna, in about 8 m. 
above the present level of the water.! E. v. Martens recognized that these 
subfossil shells belonged to species still Living nowadays in the lake. The 
most abundant among them are Corbicula radiata, Melanoides tuber- 
culata, Planorbis choanomphalus, and Bulimus alberti, but many others 
are also present. Gromier also collected them from deposits near 
Vichumbi, 5 m. above the level of the lake,? and the junior author found 
them in hardened marls more to the east, near Kabare. 
1In 1894 (‘ Mit Emin Pasha ins Herz von Afrika,’ I, p. 270) Stuhlmann describes these deposits as 
follows: “ Die Ebene besteht, so weit wir sie durchmessen haben, aus schwirzlichen Ablagerungen, in 
denen sich zahlreiche Schneckenschalen finden. Noch in ziemlicher Entfernung vom See fanden wir 
westlich von Vitshumbi etwa 1 m. unter der Oberfléche eine 4-6 cm. starke Schicht, die mit Schalen von 
Siisswassermollusken (Planorbis, Unio, Melania und anderen) durchsetzt war. Nach unsere Schatzung 
lag dieser Schicht etwa 8 m. tiber dem heutigen Wasserspiegel; tiber ihr hatte sich ein graubrauner 
Thon Coe Be 
Germain (1916, Bull. Mus. Hist. Nat. Paris, Pl. v) has published a photograph of a li i 
embedded fresh-water shells, obtained by Gromier near aay 2 rae peeene ete 
