— 6o — 



Unio (Nodularia) caesariana sp. n. — PI. IV, fig. g 



Shell allied to Unio nyassamts Lea, but differing from that species in 

 its paler colour, more elongate and rectangular form and finer, much more 

 diffused and more noticeable sculpture. 



Long. 22, lat. 31, diam. 14.5 mm. 



Hab. — Lake Nvassa. 



Unio (Nodularia) luapulaensis sp. n. — PL IV, fig. 11. 



Shell moderately conves and thin, ovate, covered with a blackish-brown 

 periostracum becomiug somewhat scabrous posteriorly, marked with 

 coarse, concentric growth striae and posteriori)^ sculptured above onl)^ with 

 fine, radiate ridges; umbones much eroded, not prominent, smooth; dorsal 

 margin arched and sloping; ventral margin slightl)^ rounded; anterior side 

 rather obtusely angled above and rounded below; posterior side sloping 

 above, acutely rounded below; right valve bearing a nearly straight, erect, 

 latéral tooth wich has a-fine, roughened, file-like appearance above, and 

 two slightly elongate, rather oblique, parallel, cardinal teeth, the inner of 

 which is the shorter, larger, and more erect and is also jagged along the 

 upper edge; left valve bearing a long, bifurcating, latéral tooth and two 

 cardinals of which the anterior is much the larger, erect, sloping posteriorly, 

 roughened on both sides, jagged above and broadening out into a roughened 

 shelf, below which the posterior is small, roughened at the sides, but 

 scarcely jagged above and slightty overhanging the interior of the shell; 

 anterior muscular scars very deeply impressed, posterior scars very lightl}^ 

 marked; interior of shell nacreous, pinkish, shadiug to bluish at the lower 

 posterior side, showing traces of radiate striae, especialh'- posteriorly and 

 very slightly granular towards the umbonal cavity. 



Long. 25, lat. 40.5, diam. 15 mm. 



Hab. — Confluence of the Lukulu and Luapula Rivers, Belgian 

 )ngo. 



Unio (Qrandidieria) tanganyicencis, Smith (') var. exalbida 



Congo 



var. n. 



Shell differing from the tj^pical form in its almost white, though irides- 

 cent, interior and in being esteriorly covered with a pale yellowish perios- 



(') Proc. Zool. Soc, London, 1880, p. 351, pi. XXXI, fig. 9-9". 



