1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 131 
PLANORBULA Haldeman 
Discus HALDEMAN, July, 1840, ‘Monograph of Limniades of North America,’ 
pt. 1, p. 4 of cover (not Discus of Fitzinger, 1833). Monotype: Planorbis armigerus 
Say. 
Planorbula HALDEMAN, October, 1840, op. cit., Suppl. to part 1, p. 2 (new name 
for Discus Haldeman); 1842, op. cit., IV, Physade, p. 14. Monotype: Planorbis 
armigerus Say. . 3 
Coretus subgenus Dentatus ‘‘Beck”’ Gray, 1847, Proc. Zoél. Soe. London, p. 181. 
Monotype: Planorbis armatus Gray, supposed to be Planorbis armigerus Say. 
Haldemanina Dauu, 1905, ‘ Alaska,’ XIII, p.97. Monotype: Planorbis wheatleyt 
Lea. : 
Planorbulina KE. v. Martens, 1899, ‘Biologia Centrali-Americana, Land and 
Fresh-water Mollusca,’ p. 400. Hos the group of Planorbis armagerus Say: ; evidently 
a clerical error for Planorbula. 
Shell small, planorboid, ec eae showing the spiral broadly on both sides, 
deeply concave on the left side, nearly level on the right; whorls broadly rounded 
peripherally, angular or rounded on the left side. There is at some time in life an 
internal barrier in the throat composed of five or six transverse and entering teeth; 
these may, however, be resorbed in the course of growth so that in adult specimens 
there is often only one lamella and in some specimens the throat is unarmed. In the 
adult the aperture is margined internally with a thickened, whitish rib. 
The genus is only known from America and the Ethiopian Region. 
It is especially numerous in tropical America. The African species 
appear to be very closely related. 
Planorbula alexandrina (Ehrenberg) =Planorbis alexandrinus Ehrenberg, 1831, 
‘Symbole Physice, Evertebrata, I, Mollusca,’ p. [18]. Planorbula jickelit Bour- 
GUIGNAT, 1876, Bull Soc. Sc. Phys. Nat. Bordeaux, p. 80. Planorbula alexandrinensis 
Grermatn, 1923, Rec. Indian Mus., XXI, p. 182. Type locality: between Alexandria 
and Rosette, Lower Egypt. The species is known from Egypt to Eritrea, and we 
have seen specimens from the-Bahr-el-Ghazal, Lake Abaja in Abyssinia, and Lake 
Rudolf. 
Planorbula boccardi PonboNERA, 1898, Boll. Lab. Zool. Anat. Comp. Torino, 
XIII, No. 313, p. 11, Pl., figs. 22-25. Adi-Ugri, Eritrea. 
Planorbula tanganyicensis (E. A. Smith). See below. 
Planorbula tchadiensis Gmrmatn, 1904, Bull. Mus. Hist. Nat. Paris, p. 468; 
1908, in A. Chevalier, ‘L’ Afrique Centrale Francaise,’ p. 510, Pl. v, figs. 8-9. Kuri 
Archipelago, Lake Chad. 
Planorbula tchadiensis var. inermis GERMAIN, 1911, ‘Doc. Scientif. Miss. Tilho,’ 
II, p. 193. Pl. 1, fig.19. Am Raya, Bahr el Ghazal. 
Species of Planorbula Recorded from the Belgian Congo 
Planorbula tanganyicensis (E. A. Smith) 
Segmentina (Planorbula) alexandrina var. tanganyicensis KE. A. Smiru, 1881, Proc. 
7061. Soc. London, p. 294, Pl. xxx1v, figs. 30-300. | 
Planorbis alecandrinus var. tanganyicensis HH. A. Smith. E. v. MARTENS, 
1897, ‘Deutsch Ost Afr., IV, Beschalte Weichth.,’ p. 150. 
