OCR Text |
Show 186 MOLLUSCA OF THE THIRD TANGANYIKA EXPEDITION. [Mar. 6, strongly spirally striated than other examples which have been examined. 5. UNIO LOURDELI Bourguignat. Hab. Dredged in about a fathom in the harbour. 6. CORBICULA CUNNINGTONI, sp. n. (Plate X. fig. 15.) Shell small, irregularly ovate, almost equilateral, moderately convex, sculptured with rather distinct and distant concentric ridges, which become almost obsolete on both dorsal slopes ; valves yellow olivaceous, with or without a few brownish rays, more or less deep purplish within; umbones prominent. Length 12g millim., diam. 8, height 11. Hab. Dredged in about a fathom in the harbour. This species may be separated from C. radiata Parreyss, the only species recorded from the Lake, on account of its somewhat different form, the umbones being more prominent, the more distant concentric ridges, and a difference in colour. None of the specimens exhibit the characteristic 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 different in the two valves. 7. SPHJERIUM VICTORLE, sp. n. (Plate X. fig. 16.) Shell roundly subovate, nearly equilateral, greyish yellow, with numerous radiating dark hair-like lines; valves thin, finely concentrically striated with the lines of growth, which are crossed 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. 85. Hab. Dredged in about a fathom in the harbour. Larger than S. nyanzce Smith, not quite the same shape, different in colour, rayed, and with more delicate hinge-teeth. 8. iETHERiA ELLIPTICA Lamarck. Hab. 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. Paramelania damoni: p. 182. 7, 8. „ erassigranulata : p. 182. 10. Lavigeria grandis: p. 182. 11. „ „ operculum. 12. Anceya rtifocincta : p. 183. 13. Criraudia horei, operculum : p. 183. 14. „ preeclara, operculum : p. 183. 15. Corbicula cunningtoni{: p. 186. 16. Sphcerium victorice: p. 186. 17, 18. Ancylus tanganyicensis: p. 184. 19. Edgaria nassa, operculum : p. 182. |