586 UNIO 
rather solid pseudocardinal in the right valve, deeply incised, 
two in the left : nacre vellowish-white ; muscle scars deep. Ani- 
mal unknown. 
UNIO KUNENENSIS Mousson. 
Shell irregularly elliptical or subovate, inequilateral, subin- 
flated, solid; beaks moderately full and elevated; posterior 
ridge somewhat double, ending behind about on the median 
line in a distinct biangulation; dorsal outline curved; anterior 
end rounded; base straight to behind the middle where it is 
angled and obliquely truncated to the posterior end; dorsal 
slope obliquely truncated; surface covered with irregular, 
somewhat granulose, concentric sculpture, which in places be- 
comes zigzagged ; epidermis apparently brownish; teeth rather 
strong; nacre bluish-white, salmon-tinted in the cavities; an- 
terior muscle scars deep. 
Length 38, height 25, diam. 23 mm. 
Head of Kunene River, North Ovampo, Southwest Africa. 
Unio kunenensis Mousson, Jl. de Conch., XXXV, 1887, p- 
300, pl. x11, fig. Io. 
Nodularia kunenensis SIMPSON, Syn., 1900, p. 824. 
The distinct posterior biangulation, and the peculiar sculp- 
ture varying from granulous concentric to zigzag will distin- 
guish this species from others. The,statement made by Mous- 
son that the length of this shell is 28 millimeters is no doubt 
an error, as the figure shows it to be 38. 
Section E1.iprio Rafinesque, 1810. 
Elliptio Rarinesgur, J.. de Phys., Chimie, Hist. Nat., 
LXXXVIII, 1819, p..426—OrtMann, Ann. Car. Mus. VIII, 
1OI2, p. 265. 
Shell elongated, rhomboid or oval, usually more or less bi- 
angulate behind; beak sculpture consisting of a few rather 
strong ridges, which are nearly parallel to the growth lines 
or slightly doubly looped; the surface smooth or feebly corru- 
gated. 
Type, Unio crassidens Lamarck. 
Ortmann, (1. c.), raises this group to generic rank. 
