584 UNIO 
or young caffer, but is higher in proportion to its length and is 
not inflated. 
The following unfigured species is said to belong here: 
Unio mandinguoruwm RocHEBRUNE, Bull. Soc. Phil., 7th ser., 
Ni, 1882, p: 34. 
Bakoy, Upper Senegal. 
Group of Unio fissidens. 
Shell solid, compressed, subelliptical to subrhomboid, with 
rather full beaks, which have radiate, corrugate sculpture ex- 
tending out on the disk as wavy sulcations, and changing near 
the edge to plain sulcations; posterior ridge low, rounded; 
hinge strong; right valve with two pseudocardinals, the lower 
the larger, showing a tendency to split up, and having a gape 
in the plate behind, and having one lateral; two pseudocardi- 
nals in the left, somewhat split, and two laterals; muscle scars 
deep, distinct. 
Unio FISSIDENS Bettger. 
Shell subrhomboid, a little higher in front, inflated, solid 
and strong, inequilateral; beaks considerably elevated, almost 
pointed, their sculpture consisting of rugose, wavy or zigzag 
bars, which gradually change farther down on the disk to 
strong, concentric ridges; anterior end rounded; base nearly 
straight ; dorsal line behind the beaks very slightly curved, 
rounding into the obliquely subtruncate posterior slope; pos- 
terior ridge rounded, ending in a rounded point near the base; 
pseudocardinals of the left valve split up into several radial 
denticles, those of the right divided into three, with a triangu- 
lar pit behind them; laterals strong, nearly straight; muscle 
scars deep. 
Length 53-58, height 28.5-33, diam. 20-28 mm. 
Kalahari Desert. Southwest Africa. 
Unio (Hyridella) fissidens Bovrcrer, Ber. Senck. Ges., 1886, 
Po 27; pleitanss. 6a, 6b -7a4gp. 
Unio fissidens CONNOLLY, Ann. S. A. Mus., XI, 1912, p. 274. 
Nedularia fissidens StMpson, Syn., 1900, p. 827. 
