1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 139 
regularly arcuate. Columella slightly concave, reflected over, but not 
closing the perforation. 
Length, 2.85 mm.; diameter, 1.7 mm.; aperture, 1.55 mm.; 3% whorls. 
Some larger specimens in the same lot (Figs. 120, c) differ somewhat 
in contour, are more strongly sculptured, and have the aperture narrower. 
These may possibly represent a different species—a point to be deter- 
mined by further collecting and observation in the original locality. — 
Figure 12c measures: 
Length, 4.4 mm.; diameter, 2.3 mm.; aperture, 2.3 mm.; 4% whorls. 
| 
a 
) 
iN 
Fig. 12. Bulinus senegalensis O. F. Miller. a, typical. b-c, larger form- 
Marsh of Podor, Senegal. 
Species of Bulinus, proper, Recorded from the Belgian Congo 
Bulinus coulboisi (Bourguignat) 
Physa coulboisi BourGuIeNaAtT, 1888, ‘Iconogr. Malacol. Tanganika,’ Pl. b 
figs. 24.and 25; 1890, Ann. Se. Nat. Zool., (7) X, p. 14, Pl. 1, figs. 24 and 25. 
Isidora coulboisi Bourguignat. E. v. Martens, 1897, ‘Deutsch Ost Afr., IV, 
Beschalte Weichth.,’ p. 139. E. A. Smrru, 1904, Proc. Malacol. Soc. London, VI, 2, 
p.99. Ancry, 1907, Bull. Scientif. France et Belgique, (5) IX, (1906), p. 249. 
Physa (Isodora) coulboisi Bourguignat. Gmrmatn, 1905, Bull. Mus. Hist. Nat. 
Paris, p. 255; 1908, ‘Rés. Scientif. Voy. Afrique Foa,’ p. 640. 
Lake Tanganyika: originally described from the western shore of the lake, 
without more definite locality. 
Bulinus randabels (Bourguignat) 
Physa randabeli BoureuicNat, $888, ‘Iconogr. Malacol. Tanganika,’ PI. 1, 
figs. 26 and 27; 1890, Ann. Sc. Nat. Zool., (7) X, p. 12, Pl. 1, figs. 26 and 27. 
Isidora randabeli Bourguignat. E. v. Marrens, 1897, ‘Deutsch Ost Afr., IV, 
Beschalte Weichth.,’ p. 140. E. A. Smrru, 1904, Proc. Malacol. Soc. London, VI, 
2,p.99. Ancry, 1907, Bull. Scientif. France et Belgique, (5) IX, (1906), p. 249. 
Lake Tanganyika: Ubuari Peninsula (type locality). 
Subgenus PyRGopHysa Crosse 
Pyrgophysa Cross, 1879, Journ. de Conchyl., XXVII, p. 208. Monotype: 
Pyrgophysa mariei Crosse, of Nossi Bé. 
