404 . Bulletin American Museum of Natural History [Vol. LIII 
Unio (?) briarti Dautzenberg. Stmpson, 1914, ‘Descript. Cat. of Naiades,’ p. 719. 
Unio eduardi “Dupuis” DautzENBERG AND GeRMaIN, 1914, Rev. Zool. Afric., 
IV, 1, p. 68 (asa synonym of U. briariz). 
Lofoi River (type locality; Briart Coll.). Lower Ubangi at Zongo (Poutrin 
Coll.). Lualaba River at Kibombo (J. Bequaert Coll.). 
We have seen a young shell collected by the junior author at Kibombo 
and determined by Dautzenberg. It shows beaks having two series of 
tubercles; and up to a length of 20 mm. the anterior and posterior dorsal 
slopes are strongly corrugated. 
Subgenus Lavirostris Simpson 
Diplodon subgenus Levirostris Stmpson, 1900, Proc. U. 8. Nat. Mus., XXII, p. 
894. Monotype: Unio stagnorum Dautzenberg. 
Beaks unsculptured except for minute, concentric striz. 
The subgenus Levirostris Simpson was originally placed under the 
South American genus Diplodon, a genus otherwise unknown in Africa. 
We hesitate to accept this classification for the reason that in all other 
characters the shell agrees well with Cexlatura. In some species of 
Cexlatura, such as C. rotula, the beaks have only faint, though still legible 
traces of tubercles. Temporarily, therefore, until the soft anatomy can 
give evidence, we subordinate Levirostris to Celatura. 
Celatura (Levirostris) stagnorum (Dautzenberg) 
Plate XX XIII, Figures 1, la, 1b 
Unio stagnorum DautTzENBERG, 1891, Bull. Ac. Sci. Belgique, (8) XX, (1890), 
p. 572, Pi. 1, figs: 7-10. 
Celatura stagnorum Dautzenberg. C. R. Barremr, 1913, Ann. Soc. Zool. 
Malacol. Belgique, XLVIT, (1912), p. 111. | 
Diplodon (Levirostris) stagnorum Dautzenberg. Simpson, 1900, Proc. U.S. Nat. 
Mus., XXII, p. 894; 1914, ‘Descript. Cat. of Naiades,’ p. 1309. 
Between Vivi and Isangila near the confluence of the Mpakassa (type locality; 
E. Dupont Coll.). Boma (De Jong Coll.). 
Zambi (Lang and Chapin Coll.). Boma (J. Bequaert Coll.). 
The shell is thin, subtriangular, the height about 67 to 74 per cent of the length, 
rather convex; deep olive-buff, the lower half or less colonial buff. The dorsal margin 
is only slightly conyex; anterior end narrowly rounded; posterior margin nearly 
straight, oblique, almost as long as the dorsal margin; the basal margin is convex, the 
curvature greater toward the ends, slight (or sometimes nearly straight) in the middle. 
The beaks are small, moderately elevated, slightly in advance of the anterior fourth 
of the length; they are eroded in even the smallest specimens seen (18 mm. long, the 
eroded areas 2.1 mm. long); no sculpture except thread-like concentric striz is visible. 
Posterior ridge rounded. Posterior slope very wide, flattened or slightly concave. 
The surface is finely striate, the strie laminiferous toward the margins and on the 
