1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 353 
Lake Tanganyika: we have seen numerous, mostly wave-worn 
valves collected by Stappers, without more definite data. In the Congo 
Museum at Tervueren there are other specimens referred to this species 
by Dautzenberg and obtained by the same collector from the beach 
between Mwerasi and Kapampa; these we have not seen. 
This species was figured but not described by Bourguignat. It is a 
quite small, ventricose clam, well distinguished by its short, high form, 
the height about equal to the length, and by the very wide, obtuse 
beaks. Externally it is distinctly striate, the strie fine and not very 
close. The hinge-plate and teeth are unusually heavy. The right valve 
has an arched cardinal tooth, bifid posteriorly and slightly so anteriorly. 
Laterals heavy and rugose, especially the posterior. In the left valve 
there is a curved posterior cardinal, thick at the posterior end, and a 
somewhat bifid, short anterior cardinal; both laterals heavy and high. 
Length, 2.4 mm.; height, 2.4 mm.; semi-diameter, 0.8 mm. 
Another species having the general outline of P. katangense is 
represented by a single valve, 2 mm. long, 1.7 mm. high, found with the 
specimens of P.hermosum. As it is somewhat worn, a description need 
not now be given. | 
Fig. 78. Pisidiwm katangense Pilsbry and Bequaert. Right valve of type. 
- Pisidium katangense, new species 
Text Figure ie 
Kisanga River near Elisabethville, 5 valves, type locality; Lubum- 
bashi River at Elisabethville, one specimen (Michael Bequaert Coll.). 
