1888.] FROM THE ALBERT NYANZA. 55 



ovata, longit. totius | hand cequans ; peristoma tenue, conti- 

 nuum, marginibus externi et basali levissime expansis. Longit. 5 

 millim., diam. 3 ; apertnra 2^ X 2. 



Fig. 3. 



Bijth'mia walleri. 



This is very different in form from B. alberti, having a much 

 higher spire and smaller aperture. The single specimen is at present 

 in the possession of the Rev. H. Waller. 



8. Planorbis sudanicus. 



PL sudanicus, v. Martens, Mai. Blat, 1870, vol. xvii. p. 35 ; 1874, 

 p. 41 ; Pfeiffer, Novit. Conch, vol. iv. p. 23, pi. 1 14. f. 6-9 ; Smith, 

 Proc. Zool. Soc. 1880, p. 349. 



Hab. White Nile {Consul Petherick in Brit. Mus.) ; Gazelle 

 River (Bahr-el-Ghasal) {v. Martens) ; Albert Nyanza {Baher and 

 Emin) ; Tanganyika {Smith). 



It is interesting to note the distrihution of this species as dimly 

 indicating a connection between the two lakes, which at present is 

 but a matter of conjecture. 



9. PLANORBtS STANLEYI, n. Sp. 



Testa mediocriter depressa, utrinque suhcequaliter concava, nitida, 

 oblique striata, vix semipellucida, cornea, inf erne pallida ; unfr ac- 

 tus 4, celeriter accrescentes., rutundati, ultimus mag7ius, antice 

 paulo injlatus, sutura profunda sejunctus ; apertura magna, 

 obliqua, plerumque supra anfr . penultimum elevata ; perist. tenue, 

 marginibus callo tenui junctis, columellari leviter incrassato et 

 reflexo. Diam. 9, alt. 4| ; apertura A\ longa, ^ millim. lata. 

 This species is remarkable for the rapid enlargement of the last 

 whorl, which ends in a very open aperture and usually is produced 

 above the penultimate whorl ; in some specimens, however, it descends 

 somewhat. 



10. Corbicula radiata, Philippi. 



Cyrena radiata (Parreyss, MS.), Philippi, Abbild. vol. ii. p. 78, 

 pi. 1. f. 8. 



Hab. White Nile (Bahr-el-Abiad) {Philippi); Albert Nyanza 

 {Baker and Emin) ; Lake Nyassa {Smith, P. Z. S. 18/7 p. 718). 



11. Corbicula pusilla, Philippi. 



Cgrena pusilla (Parreyss, MS.), Philippi, Abbild. vol. ii. p. 78, 

 pi. 1. f. 7. 



Hab. Upper part of the Nile {Philippi) ; Syene or Assouan on the 

 Nile {Parreyss in Brit. Mus.). 



