126 Bulletin American Museum of Natural History (Vol. LIIT 
Planorbis (Gyraulus) gibbonsi Nelson 
Text Figure 8 
Planorbis (Gyraulus) gibbonsi Neson, 1878, Quart. Journ. of Conch., I, p. 379, 
Pl. 1v, fig. 3 (type locality: Zanzibar Island). 
Planorbis gibbonsi Nelson. E. v. Marrens, 1897, ‘Deutsch Ost Afr., IV, Be- 
schalte Weichth.,’ p. 150. 
Planorbis (Tropidiscus) gibbonsi Nelson. DautTzENBERG AND GERMAIN, 1914, 
Rev. Zool. Afric., IV, 1, p. 42. 
Lake Albert: Kassenje (Stuhlmann Coll.). Lake Kisale at Kikondja (J. Be- 
quaert Coll.). | 
Dautzenberg and Germain synonymize with this Planorbis mutandaensis Preston, 
but we have been unable to find the description of that species. 
a rear <) 
4™mm 
Fig. 8. Planorbis gibbonsi Nelson. Kabare, Lake Edward. 
Lake Edward: Kabare (J. Bequaert Coll.). 
Specimens which we refer to this species were found with P. foula- 
dougouensis, from which they are readily distinguishable by the wider 
spire and the smoother surface, which is merely striatulate. The width 
of aperture is a little less than one-third of the total diameter. These 
examples are somewhat smaller than the typical P. gibbons: compared, 
but do not seem to differ otherwise. Two figured measure: 
Diameter, 2.80 mm.; altitude, 0.8 mm.; 3)4 whorls. 
“ 3.15 on hs a 3 
Planorbis (Gyraulus) fouladougouensis Germain 
Planorbis (Paraspira) fouladougouensis GERMAIN, 1917, Bull. Mus. Hist. Nat. 
Paris, p. 523, PI. vir, figs. 6-8 (type locality: Tukoto, in the Bakoy River, Senegambia). 
Lake Edward at Kabare (J, Bequaert Coll.). 
A prominent feature of this species is the sculpture of close rib-strie. 
The spire is narrower than in P. gzbbonsi, and the last whorl on the right 
side is decidedly wider than in P. misellus Morelet. The width of the 
aperture exceeds one of the total diameter. Diameter, 3.1 mm.; 
altitude, 0.9 mm.; 3% whorls. 
Planorbis istinieees Preston, from Lake Victoria, must be a good 
deal like these specimens, but the description and figure are insufficient 
for decision. P. sperabilis Preston also seems to be related. 
