580 UNIO 
anterior end rounded or subtruncate ; base line straight or near- 
ly so; hinge line lightly curved; dorsal slope with a long, de- 
cided, oblique truncation; posterior: ridge very full, narrowly 
rounded, ending at or near the base in a blunt point; surface 
generally having light, concentric growth lines, those becom- 
ing stronger and somewhat broken at the anterior end; epi- 
dermis yellowish-green ; teeth rather delicate ; pseudocardinals. 
subcompressed ; nacre whitish, iridescent. 
Length 20, height 15, diam. 10 mm. 
Lake Albert Nyanza. 
Unio acuminatus H. Apams, Pr. Zool. Soc. Lond., 1866, p. 
376.—SMiTH, Ann. and Mag., X, 1892, p. 127, pl. xu, fig. 
12.—vVON MArrtENS, Besch. Deuts. Ost. Af., 1897, p. 227, pl. 
Vil, ies. 11, D2 
Nodularia acuminata SIMPSON, Syn., 1900, p. 826. 
Distinguished by its decidedly rhomboid form, the high, 
narrowly rounded posterior ridge and the strong, zigzag, nod- 
ulous beak sculpture that extends out on to the disk. 
UNIO DEMBE Reeve. 
Shell somewhat elongated, subrhomboid or subelliptical, sub- 
inflated, solid, inequilateral ; beaks moderately full and high; 
posterior ridge full, more or less double, ending behind in a 
biangulation at and below the median line; dorsal outline ir- 
regularly curved; anterior end rounded, slightly angled above ; 
base line lightly curved; posterior slope obliquely subtruncated ; 
surface with light concentric sculpture; dorsal slope with a 
few feeble plications ; epidermis fulvous-olive, tinged and ray- 
ed with green; teeth moderately strong, swbcompressed ; mus- 
cle scars deep ; nacre pale flesh-color. 
Length 66, height 32.75, diam. 21.5 mm. 
Length 59, height 29, diam. 19.5 mm. 
Abyssinia. 
Unio dembee Reve, Conch. Icon., XVI, 1865, pl. Xx1x, fig. 
153.—JICKEII, Faun. Moll. Af. 1874, p. 275, pl. 1x, figs. 3-4. 
Nodularia dembee@ Stuvson, Syn., 1900, p. 826. 
