1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 405 
posterior slope. Color ecru-olive with faint green rays on the posterior convexity and 
slope. The interior is light blue. Pseudocardinal teeth thin, compressed; in the 
right valve double, of equal length, but the lower one is thicker and much higher. 
The edges are weakly crenulate. The left valve has a single, rather high pseudo- 
cardinal and a slight widening of the narrow interdental area below the beaks. The 
lateral teeth are thin, rather short but well developed, double in the left, single in the 
right valve. The hinge line is rather strongly curved. The anterior adductor scar is 
well impressed, the scar of the foot protractor small, separate. The ligament is narrow. 
Length, 44.0 mm.; height, 30.0 mm.; diameter, 17.0 mm. 
e425 Rete + PS y 16.0 
oO Fe ae 3 16.0 
‘EARS ORO i, 18.0 
The elevated, triangular shape of this thin species is characteristic. 
Beak sculpture, if present, must occupy an extremely small space. 
Most specimens are more or less colored by the iron deposit, as shown 
in Dautzenberg’s excellent figures; when cleaned of this the shell is 
deep olive buff in the older part, becoming straw or colonial buff in the 
last half or third of the height. } 
Celatura (Levirostris) stagnorum bome, new subspecies 
Plate XX XIII Figures 2 and 2a 
Congo River at Boma (J. Bequaert Coll.). 
The shell is similar to C. stagnorum except that on both sides of the eroded beaks 
there is well-developed corrugation running toward the hinge-margin. 
Length, 38 mm.; height, 26 mm.; diameter, 12.5 mm. 
The sculpture of this form would not be considered of much im- 
portance were it not entirely absent in long series of C. stagnorum from 
Zambi, and several from. Boma. 
Celatura (Levirostris?) rotula, new species 
Plate XX XIII, Figures 5 and 5a 
Congo River at Leopoldville (J. Bequaert Coll.). 
The shell is thin, very broad, moderately convex. The dorsal and basal margin 
are somewhat convex; the anterior end rather narrowly rounded; posterior end 
straight in its upper part, then broadly rounded. The beaks are small, project but 
little and are eroded in the type; on the anterior side there are a few short, curved 
corrugations running foward the hinge. ‘The rest of the shell is smooth except for 
numerous narrow, irregular corrugations diverging upward from the rounded, posterior 
ridge. Surface is glossy, becoming dull and slightly laminate at the ends. . Color 
ecru-olive, varying toward lighter or greener, the posterior slope duskier, with one — 
or two green rays. The interior is very pale blue. Hinge line gently curved. Pseu- 
docardinal teeth are long and very much compressed; in the right valve two, sub- 
equal; in the left single. Laterals are short, compressed. The anterior adductor 
sear is a little impressed. bodae tues | Te sagt: 
