1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 129 
Hemithalamus ‘‘Leach” Turton, 1831, ‘Manual Land Fresh-water Shells Brit. 
Isl.,’ p. 116. Asasynonym of Segmentina nitida. 
Planorbis subgenus Segmentaria Swainson, 1840, ‘Treatise «n Malacology,’ 
p. 837. Monotype: S. lacustris Fleming = Planrobis nitidus O. F. Miller. Evidently 
a clerical error for Segmentina. 
Shell small or minute, planorboid, glossy; the whorls deeply embracing, the last 
very large and carinate or angular; aperture lunate or subtriangular. Cavity of the 
last whorl divided by several barriers, each typically composed of three transverse 
laminze, on parietal, upper, and basal margins, leaving a triramose passage. In some 
forms these laminz are more numerous, or they may be much reduced, or the parietal, 
or parietal and upper ones may be wanting. 
This genus differs from Planorbula by having the spire very narrow on 
both sides, especially on the left, where the whorl is broadly rounded, 
the angulation or zone of greatest convexity of the whorl being pe- 
ripheral, while in Planorbula the periphery is rounded. In addition, the 
internal barriers are all transverse to the cavity and more than one set 
is usually present. The embryonic whorl has spiral lines of punctures, 
as in the subgenus Hippeutis, which Segmentina, moreover, resembles in 
general shape and from which stock it may have been derived. 
Segmentina is restricted to the Old World. The following Ethiopian 
species have been described. 
Segmentina angusta Jickeli. See below. 
Segmentina emicans (Melvill and Ponsonby) =Planorbis (Segmentina) emicans 
MELVILL AND PonsonBy, 1892, Ann. Mag. Nat. Hist., (6) X, p. 241, Pl. xm, figs. 
13-13a. Zwartkop, Cape Colony. | 
Segmentina eussoensis Preston, 1912, Proc. Zodl. Soc. London, I, p. 191, Pl. 
xxxul, figs. 6 and 6a-b. Chanler Falls, Eusso Nyiro, Kenya Colony. 
Segmentina kanisaénsis Preston, 1914, Journ. Linn. Soc. London, Zool., XXXII, 
p. 265, Pl. xvi, figs. 17-19. In the Nile at Kanisa. 
Segmentina kempi Preston. See p. 130. 
Segmentina planodiscus (Melvill and Ponsonby) =Planorbis (Segmentina) 
planodiscus MELVILL AND PonsonBy, 1897, Ann. Mag. Nat. Hist., (6) XIX, p. 638, 
Pl. xvut, fig. 10. Umgeni River, Natal. 
Segmentina angusta “EH. v. Martens” Jickeli 
Text Figure lla, 6, c 
Segmentina angusta E. v. Martens, 1873, Malakoz. Blatter, XXI, p. 42 (nomen 
nudum). Jicxext, 1874, Nova Acta Ac. Nat. Cur. Dresden, XXXVII, 1, p. 220, 
Pl. vu, figs. 24a-c (type locality: Toquor River at Mekerka, Abyssinia). DautzENn- 
BERG AND GERMAIN, 1914, Rev. Zool. Afric., IV, 1, p. 48. 
Segmentina chevalieri GERMAIN, 1904, Bull. Mus. Hist. Nat. Paris, p. 468; 1905, 
op. cit., p. 256; 1908, ‘Rés. Scientif. Voy. Afrique, Foa,’ p. 639, figs. 6-7 (type locality: 
Lake Chad). 7 
Lake Kisale at Kikondja (J. Bequaert Coll.). Lake Tanganyika: at the south- 
ern end (Foa Coll.; recorded as S. chevaliert). 
