— 6i — 



tracum which, ho'ïveTer, still faintly shows the green radiate bands of the 

 tA-pical form. 



Long. 17.75, ^'^t. 24.5, diam. 11.5 mm. 



Hab. — Lake Tanganvika. 



Mutela lukuluensis sp. n. — PI. VI, fig. 4. 



Shell moderately convex, elongately, ovately cuneiform, brown, gloss}-, 

 except on the posterior third portion •where the periostracum becomes dull 

 and somewhat scabrous, marked with moderately fine, concentric giowth 

 lines and ladiatelv striate in the médian and anterior régions ; umbones not 

 prominent; dorsal margin ver}* gently arched and sloping; ventral margin 

 nearly straight, A"er}" slightly contracted in the médian part; anterior side 

 rounded; posterior side sloping above, bluntly rostrate below; muscular 

 scars ovate well impressed; interior of shell dark bluish iridescent. 



Long. 24.5. lat. 50.25, diam. 13 mm. 



Hab. — Confluence of the Lukiilii and Liiapula Rivers, Belgian 

 Congo. 



Mutela saraesp. n. — PL VI, %. 6. 



Shell rather convex, elongately subrectangular, covered vrith a chocolate- 

 coloured periostracum which becomes somewhat finely laminiferons towards 

 the ventral margin and posterior side and shows traces of radiate striae; 

 umbones slightly prominent; dorsal margin %"er\' gently sloping; ventral 

 mai-gin almost straight, a little contracted in the médian part; anterior side 

 rounded; posterior side sloping above, somewhat rostrate below; muscular 

 scars ovate, anteriorly deeply impressed, posteriorly lightly so ; interior 01 

 shell nacreous, pale pinkish-purple. 



Long. 27, lat. 57.5, diam. 17 mm. 



Hab. — Shire River^ near its outflow from Lake Nvassa. 



Mutela mathildae sp. n. — PL VI, fig. 7. 



Shell allied to M. sarae, but more convex and ovate, the colom^ is dark 

 olive-green shading to chocolaté towards the margins and the radiate striae 

 are more apparent; the dorsal margin is rather more sloped and the ventral 

 margin slightly rounded, though contracted in the anterior médian région; 

 the anterior side is more rounded above and sloping below and the posterior 



