1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 175 
Width of the central tooth, 0.5 mm. It is much like the teeth of Ameri- 
can species figured by H. Burrington Baker! 
The determination of African Pilz is difficult because of the simi- 
larity of the species. The minute sculpture, the width of the aperture, 
and the length of the adnate portion of the inner lip relative to that of 
the aperture, have been found to be among the most useful differential 
characters. In some cases the relative width of the operculum and its 
scar is highly characteristic. The sculpture of the scar is rather variable 
individually, and it changes somewhat with age. _ 
The following is a list of continental African forms which appear 
to be specifically distinct. Most of them have been insufficiently 
described. 
Pila africana (EK. von Martens) =Ampullaria africana E. von Manrrens, 1886; 
Sitz. Ber. Ges. Naturf. Fr. Berlin, p. 114. Gold Coast (Abetifi and Akra). 
Pila chariensis (Germain) = Ampullaria chariensis GERMAIN, 1905, Bull. Mus. 
Hist. Nat. Paris, p. 486; 1906, Mém. Soc. Zool. France, XIX, p. 232, Pl. 1v, fig. 10. 
Lower Chari between Buguman and Fort Lamy; also-Lake Chad. 
Pila charmesiana (Billotte)=Ampullaria charmesiana Biuuorre, 1885, Bull. 
Soc. Malacol. France, II, p. 106. Ampullaria wernei Puiuipri (in part), 1851, in 
Martini and Chemnitz, ‘Syst. Conch. Cab.,’ I, 20, Pl. v, fig. 4. Nile, above Gondo- 
koro. 
Pila chevaliert (Germain) = Ampullaria chevalieri GeRMaAIN, 1904, Bull. Mus. Hist. 
Nat. Paris, p. 469; 1908, in A. Chevalier, ‘L’ Afrique Centrale Francaise,’ p. 525, 
fig. 89 (on p. 526). Krebedje, French Equatorial Africa; this was apparently found 
in the Congo drainage. 
Pila congoensis Pilsbry and Bequaert. See p. 177. 
Pila congoensis amplior Pilsbry and Bequaert. See p. 179. 
Pila gordont (KE. A. Smith) =Ampullaria gordoni E. A. Smiru, 1892, Ann. Mag. 
Nat. Hist., (6) X, p. 882. Lake Victoria. 
Pila gordont var. bukobe (E. v. Martens)=Ampullaria gordoni var. bukobe 
E. v. Martens, 1897, ‘Deutsch Ost Afr., IV, Beschalte Weichth.,’ p. 156, Pl. 1, 
fig. 22. Lake Victoria at Bukoba. ) 
Pila gordoni var. volkensi (E. v. Martens) = Ampullaria gordoni var. volkensi E. 
v. Martens, 1897, ‘Deutsch Ost Afr., IV, Beschalte Weichth.,’ p. 157. Lake Jipe 
near Mt. Kilimanjaro. : 
Pila gradata (EK. A. Smith) = Ampullaria gradata E. A. Smiru, 1881, Proc. Zo6l. 
Soc. London, p. 289, Pl. xxxutt, figs. 22 and 22a. Lake Nyasa and between Lake 
Nyasa and the east coast. Germain (1905, Bull. Mus. Hist. Nat. Paris, p. 256; 
1908, ‘Rés. Scientif. Voy. Afrique Foa,’ p. 670) records this species from the southern 
end of Lake Tanganyika (Foa Coll.). 
Pila kordofana (Philippi) = Ampullaria kordofana Puiurprt, 1851, in Martini and 
Chemnitz, ‘Syst. Conch. Cab.,’ I, 20, p. 44, Pl. x111, fig. 1. Kordofan. This does not 
seem to differ very materially from Pila wernet (Philippi). 
Pila leopoldvillensis (Putzeys). See p. 180. 
11922, Occas. Pap. Mus. Zool. Univ. Michigan, No. 106, Pl. xv, figs. 6, 7. 
