1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 239 
rather weakly convex, but with well-impressed suture. Aperture ovate, the outer lip 
thin. Columella but little calloused, weakly folded. Parietal callus thin. No palatal 
fold seen in a specimen opened. 
Length, 4.3 mm.; diameter, 1.2 mm.; length of aperture, 0.8 mm.; 85 whorls. 
Type; apex broken. ? 
Length, 3.9mm.; diameter, 1.0 mm.; 8 whorls. Paratype. 
This form is quite distinct from those described by its slender shape 
and much weaker columellar fold. Though weaker, the system of sculp- 
ture is substantially as in S. m. carinifera. 
Some smaller, immature examples, length about 3 mm., have three 
or four spiral threads and the whorls are more convex. In some others 
of similar size the threads are very small, and disappear on the later 
whorls, which are smooth and rounded. 
A species from Kasakalawe, to be described, we believe, by M. 
Dautzenberg, is stouter in figure, the spiral cords are very strong, and 
the columellar fold even weaker than in S. gracilis. 
Anceya Bourguignat 
Anceya BoURGUIGNAT, 1885, ‘Notice Prodrom. Moll. Giraud Tanganika,’ p. 14. 
Monotype: Anceya giraudi Bourguignat. 
This group of beautiful little shells is distinguished from Syrnolopsis 
solely by the possession of axial sculpture. The columellar fold is usually 
shorter than in Syrnolopsis, only in the last two whorls, or weakly in one 
earlier. In A. bella it is often entirely wanting. The initial 1% whorls 
have axial sculpture and also two spiral angles or cords, as in the sculp- 
tured species of Syrnolopsis. In adult shells, the first whorl or two are 
generally lost. | 
- Burtonilla has the same early sculpture and later strong costation, 
leaving for that group only the differential characters of more numerous 
whorls and bluntly subangular rather than keeled last whorl—characters 
which can hardly be considered generic unless others are found in the 
soft anatomy. 
Subgenus ANcEYA, proper 
Anceya giraudi Bourguignat — 
Text Figures 32a-d, 33b, and 34a : 
Anceya giraudi BourguiGenat, 1885, ‘Notice Prodrom . Moll. Giraud Tanganika,’ 
p. 15; 1889, ‘Moll. Afrique Equator.,’ p. 118, Pl. vir, figs. 12-13. E. A. Srru, 
1904, Proc. Malacol. Soc. London, VI, 2, p. 97. ANcry, 1907, Bull. Scientif. France 
et Belgique, (5) IX, (1906), pp. 255 and 268. Grrmatn, 1908, ‘Rés. Scientif. Voy. 
Afrique Foa,’ p. 678. 
