NODULARIA 1025 
above, decidedly and somewhat obliquely truncate behind ; pos- 
terior ridge quite high, broadly rounded, ending at the -base of 
the sheli in a widely rounded or subbiangulate termination ; 
surface with fine concentric striz, subshining ; epidermis olive, 
with very numerous fine rays; pseudocardinals compressed, 
ragged; laterals nearly straight; nacre white and splendidly 
iridescent. 
Length 57, height 35, diam. 31 mm. 
Lake ‘Tanganyika. 
Unio randabeh Bourcuicnat, Un, and Ir. Tan., 1886, p. 22; 
Icon. Mal. Tan., 1888, pl. xx1, figs. 3. 4. 
Nodularia randabeli Simpson, Syn., 1900, p. 822. 
The shell figured appears to be somewhat diseased. It dif- 
fers from JN. nilotica in its greater degree of inflation, the 
fuller beaks and more brilliant nacre. 
NODULARIA ESSOENSIS (Chaper). 
Shell rather large, subinflated, slightly inequilateral, thin, 
subelliptical or subrhomboid; beaks high and full, their sculp- 
ture consisting of delicate, subnodulous, zigzag-radial ridges, 
with indications of similar sculpture on the dorsal slope; sur- 
face with irregular growth lines and faint indications of radial 
sculpture; hinge line slightly curved; anterior end narrowed 
and rounded; base line curved, quite full at or behind the 
middle ; posterior slope almost elevated into a wing and rather 
squarely truncated behind; posterior ridge full, rounded, end- 
ing about on the median line; epidermis brownish-green, feebly 
rayed, dull; teeth lamellar, delicate ; nacre bluish. 
Length 75, height 53, diam. 35 mm. 
Assini, west coast of Africa. 
Unio essoensis CHAPER, Bull. Soc. Zool. Fr., X, 1885, p. 481, 
pl. x1, figs. 8, 9. 
Nodularia essoensis Simpson, Syn., 1900, p. 822. 
This seems to be a larger species than N. egyptiaca, to which 
it is very closely related. It is duller colored and less rayed 
than that species and the surface is rougher. There is a fine 
young shell of this species in the National Museum from the 
Morelet collection taken at the type locality. 
