186 MOLLUSCA OF THE THIRD TANGANYIKA EXPEDITION. [Mar. 6, 



strongly spirally striated than other examples which have been 

 examined, 



5. Unio lourdeli Bourguignat. 



Hah. Dredged in about a fathom in the harbour. 



6. CoRBicuLA CUNNINGTONI, sp. n. (Plate X, fig. 15.) 



Shell small, irregulai'ly ovate, almost equilateral, moderately 

 convex, sculptui-ed with rathei' distinct and distant concentric 

 ridges, which become almost obsolete on both dorsal slopes ; valves 

 yellow olivaceous, with or withovit a few brownish rays, more or 

 less deep purplish within; umbones prominent. Length 12^ 

 millim., diam. 8, height 11. 



Hah. Dredged in about a fathom in the harbour. 



This species may be sepai-ated from C. radiata Parreyss, the 

 only species recorded from the Lake, on account of its somewhat 

 difierent form, the umbones being more prominent, the more 

 distant concentric ridges, and a difference in colour. None of the 

 specimens exhibit the characteiistic dark purple ray proceeding 

 from the umbo down the middle of the valves as in C. radiata. 

 Two out of three examples have little or no trace of markings, 

 but the third is distinctly rayed with brown, the rays being 

 difTerent in the two valves. 



7. Sph^rium victoria, sp. n. (Plate X. fig. 16.) 



Shell roundly subovate, nearly equilatei-al, greyish yellow, with 

 numerous radiating dark hair-like lines ; valves thin, finely con- 

 centrically striated with the lines of growth, which are ci-ossed by 

 minute microscopic radiating striae which are quite invisible to the 

 naked eye ; interior dirty bluish ; lateral teeth delicate. 



Length 9| millim., diam. 5^, alt. 8|. 



Hah. Dredged in about a fathom in the harbour. 



Larger than S. nyanzce Smith, not quite the same shape, 

 difierent in colour, rayed, and with more delicate hinge-teeth. 



8. ^THERiA elliptic A Lamarck. 



Hah. Entebbe, north-west end of the lake. 



EXPLANATION OF PLATE X. 



Figs. 1, 2, 3. Bythoceras iridescens : p. 182. 

 4. ,, minor : p. 182. 



5, 6, 9. Faramelania damoni : p. 182. 



7, 8. „ crassigranulata : p. 182. 



10. Lavigeria grandis : p. 182. 



11. „ „ operculum. 



12. Anceya rtifocincta : p. 183. 



13. Criraudia horei, operculum : p. 183. 



14. „ prceclara, operculum : p. 183. 



15. Corbicnla ctinningtoni\x p. 186. 



16. Sphtsriwn victoriee : p. 186. 



17, 18. Ancylus tanganyicensis : p. 184. 

 19. Edgaria nassa, operculum : p. 182. 



