UNIO 583 
in a blunt point near the base; dorsal and basal outlines nearly 
straight, parallel; anterior end rounded, cut away a little be- 
low; posterior end obliquely subtruncate ; epidermis greenish- 
chestnut; muscle scars well marked; teeth rather delicate ; 
nacre reddish. 
Length 22, height 10, diam. 8 mm. 
Lake Victoria, Nyanza. 
Unio monceti Bourcutcnat, Moll. Ny. Ouk., 1883, p. 15, figs 
13-15. 
Parreysia monceti Stmpson, Syn., 1900, p. 848. 
A considerably elongated, inflated, sulcate species, whose 
position is somewhat doubtful. It may be closely related to 
Unio caffer. I have never seen it. 
UNIo DIMINUTUS Lea. 
Shell rather small, subcompressed, subsolid, inequilateral, 
subrhomboid; beaks small, sharp, somewhat elevated, sculp- 
tured with zigzag radial ridges, this sculpture extending well 
out over the disk and gradually changing into concentric 
ridges ; dorsal outline curved ; anterior end rounded ; base near- 
ly straight to behind the middle where it is full; outline of 
dorsal slope obliquely curved; posterior ridge only moderately 
full, faintly double. ending at and below the median line in a 
slight biangulation; epidermis straw-yellow, rayless; teeth 
somewhat compressed; nacre pale, satin-like, iridescent, sal- 
mon-tinted. 
Length 33, height 20, diam. 10 mm. 
Fast Africa. 
Unio diminutis Lea, Pr. Ac. N. Sci. Phila., III, 1859, p. 151. 
Unio diminutus Lra, Jl. Ac. N. Sci. Phila., IV, 1860, p. 254, 
fp se eix tic. 134; Obs. VIP 1860p. 72, pl. xxx1rx, fig. 134. 
—ReEEvE, Conch. Icon., XVI, 1865, pl. xxvim, fig. 141. 
Margaron (Unio) diminutus Lex, Syn., 1870, p. 31. 
Nodularia diminuta StmPpson, Syn., 1900, p. 820. 
Unio gratiosus Payrer, Conch. Sam., IIT, 1890, p. 154. 
A rather short, subrhomboid, somewhat compressed species, 
quite strongly sculptured. It is something like U. vaalensis 
