UNIO 725-. 
irregular, concentric lines of growth; anterior side obliquely 
rounded; posterior side somewhat squarely rounded. 
Alt. 22.5, length 35 mm.” (Preston). 
Type locality, just above Victoria Falls, Zambesi River. 
Unio zambesiensis Preston, Pr. Mal. Soc. London, VI, 100s, 
p. 301, text-fig. 1. 
UNIO ANGONIENSIS Preston. 
“Shell ovate, slightly angled posteriorly, covered with a 
blackish-brown, lJaminiferous periostracum; sculptured with 
closely set, irregular, concentric growth-lines, and posteriorly 
with curved, transverse, interrupted, slightly nodulous riblets: 
umbones much eroded, rather large, moderately prominent : 
dorsal margin somewhat ascending, scarcely arched; ventral 
margin nearly straight; anterior side abruptly rounded; pos- 
terior side sloping above, then angled and descending sharply 
below ; lateral teeth elongate curved; cardinal tooth in right 
valve elongate, erect and jagged anteriorly, partially cleft 
posteriorly ; cardinal tooth in left valve somewhat triangular. 
broad, tuberculous in the middle, erect and jagged at the sides; 
anterior adductor scars deeply impressed, ovate; posterior 
adductor scars light ; interior of shell nacreous, pink anteriorly, 
livid bluish posteriorly. 
Length 26, lat. 39 mm.” (Preston). 
Type locality, Angoniland, British Central Africa, to the 
south of Lake Nyassa. 
Unio angoniensis Preston, Ann. Mag. Nat. Hist., (8), VI. 
1910, p. 50, pl. tv, fig. 5. 
UNIo CHARON Preston. 
“Shell elongately ovate, slightly gaping at both sides, covered 
with a black periostracum, corrugately sculptured towards the 
umbonal region and marked below with irregular, concentric 
ridges; umbones eroded, moderately large, not prominent; 
dorsal margin curved; ventral margin slightly constricted in 
the middle, otherwise straight; anterior side rather produced, 
angularly rounded; posterior side elongately produced, sharply 
rounded ; lateral teeth in both valves elongate, curved ; cardinal 
