720 UNIO 
tooth in right valve elongate, rather fine, rising considerably in 
the middle: cardinal tooth in the left almost obsolete, serrated 
anteriorly ; anterior adductor scars deep, somewhat square in 
shape; posterior adductor scars scarcely impressed. 
Length 52, height 26.5 mm.” (Preston). 
Type locality, Silongwe, British Central Africa. 
Unio charon Preston, Ann. Mag. Nat. Hist., (8), VI, 1910, 
p. (60, pl. 1%, fies 6; 
UNIo SILONGWEENSIS Preston. 
“Shell differing from U. charon by its narrower form and 
somewhat more acuminate posterior side, lighter texture, 
much smoother, concentric sculpture, and paler color, the 
periostracum being of a pale yellowish-brown color; the mus- 
cular scars are much larger and, in the case of the anterior 
adductor, more deeply impressed. 
Long: 26.5, Jat. 52 am.7).Cereston), 
‘Type locality, Silongwe, British Central Africa. 
Unio vicmus Preston, Ann. Mag. Nat. Hist., (8), VI, 1910, p. 
60; ipl ivestion 7. 
Umo silongweensis Preston, Naut., XX VI, 1912, p. 35. 
“Vicmus’ having already been used for a Unio by Lea in 
1856, Mr. Preston has proposed another name for his species. 
Unio CHOZIENSIS Preston. 
“Shell small, squarely ovate, moderately convex, covered 
with a blackish-brown periostracum, sculptured with fine, con- 
centric striae and rather coarse, transverse, corrugate ridges, 
which become finer posteriorly ; umbones not prominent; dor- 
sal margin sloping in an anterior direction; ventral margin 
slightly rounded; anterior side descending somewhat abrupt- 
ly; posterior side rather acuminately rounded; lateral teeth 
elongate, straight; cardinal teeth in right valve weak, jagged, 
erect anteriorly, bifurcate posteriorly; cardinal teeth in left 
valve elongate, finely jagged, cleft anteriorly; muscular scars 
deeply impressed anteriorly, scarcely apparent posteriorly ; in- 
terior of shell iridescent, bluish-white. 
Long 1G25elate 25mm.” “Creston ). 
