IOI2 NODULARIA 
behind, is lighter colored; it has the peculiar tubercles on the 
hinge, which seem to be lacking in Jugens, and the nacre is a 
little different. 
NODULARIA LUGENS (Drouet and Chaper). 
Shell irregularly rhomboid, narrowed in front, thin, convex, 
inequilateral; beaks moderately full and high; anterior end 
rounded, angled above; base line curved, full behind the mid- 
dle; dorsal line lightly curved; dorsal slope strongly, obliquely 
truncated, posterior ridge well developed, ending in a point 
near the base; surface nearly smooth, with some faint plica- 
tions on the dorsal slope; epidermis rich reddish-brown, sub- 
shining; teeth delicate, compressed; muscle scars shallow; 
nacre blue, iridescent behind. 
Length 54, height 32, diam. 18 mm. 
Borneo. 
Unio lugens Drourr and CHaper, Mem. Soc. Zool., Fr., V 
1892, p. 147, pl. v, figs. 1-3. 
Nodularia lugens Stmpson, Syn., 1900, p. 818. 
Contradens dimotus lugens Haas, Conch. Cab., Unio, 1912, pl. 
LO MLS ze 
The posterior ridge of the specimens I have seen is single, 
while in sacellus it is somewhat double; the nacre is deep blue 
with only a faint hint at yellowish in the beak cavities, while 
in sacellus it is lighter colored and decidedly flamed with sal- 
mon in the beak cavities. 
7 
NopuLARIA INA&OUALIS (Rochebrune). 
Shell subrhomboid, inflated, thin, inequilateral; beaks full 
and high, ornamented with granulous, angular wrinkles ; pos- 
terior ridge full, somewhat double below, ending at and below 
the median line in a faint biangulation; anterior end a very 
little narrowed, rounded: base line almost evenly curved, 
slightly fuller behind the middle: dorsal line curved; dorsal 
slope obliquely truncate; epidermis brown or green-brown; 
teeth compressed; muscle scars shallow; nacre bluish-white. 
Length 47, height 29, diam. 21 mm. 
River Srakeo, Siam. 
