1927] Pulsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 389 
The gills are three to five times as long as broad. Anteriorly the outer pair of 
gills is a little shorter than the inner, so that the margin of the latter projects beyond 
that of the former. The inner lamelle of the inner pair of gills are connected along 
more than three-fourths of their length to the abdominal sac; the posterior one-fourth 
part unites with the lamella of the opposite side to form the diaphragm; other con- 
nections of the gills are the same as in Balwantia described already [viz., the outer 
lamellz of the outer pair of gills are attached to the mantle of either side, while the 
inner lamellz of the outer pair are attached to the outer lamelle of the inner pair]. 
All the four gills are marsupial. The margin of the gills, even when full of glochidia, is 
quite sharp. The water-tubes are simple and the placente are slightly compressed, 
elongate structures. The palpi are well developed, sub-triangular with a broad base, 
along which they are attached to the abdominal mass and have the free outer angle 
rounded. The mantle has a slightly thickened entire margin. The foot is very large, 
occupying about half of the shell cavity. The branchial aperture is large, with three 
rows of small pointed papillze of a light brown color. The anal is less than half the 
size of the branchial and is marked off from it by a feebly developed ridge of the 
mantle. The supra-anal is of the same size or a little larger than the mantle con- 
nection between it and the anal. The glochidia are semi-circular or semi-elliptic. 
(1919, Rec. Indian Mus., XVI, p. 292). 
The anatomy of none of the African species thus far placed in Par- 
reysta is known and it will be of interest to learn in how far they agree 
with the above descriptions. 
Parreysia ngesiana (E. v. Martens) 
Plate XXXIJ, Figure 11 
Unio ngesianus BE. v. Martens, 1897,‘ Deutsch Ost Afr., IV, Beschalte Weichth.,’ 
p. 234, Pl. vit, fig. 7. Gmrmatin, 1916; Bull. Mus. Hist. Nat. Paris, p. 204. 
Parreysia ngesiana FE. v. Martens. Stmpson, 1900, Proc. U. 8. Nat. Mus., 
XXII, p. 847; 1914, ‘Descript. Cat. of Naiades,’ p. 1129. 
Lake Edward: Kishakka on the northwestern shore (type locality) and subfossil 
near Koha-ekjo (Stuhlmann Coll.). 
Lake Edward at Kabare (J. Bequaert Coll.). 
Two worn valves taken by the junior author agree very well with 
von Martens’ account and figure. The zigzag sculpture is developed 
over about two-thirds to three-fourths of the surface. The pseudo- 
cardinal teeth are stronger than in P. bakeri. One of these valves is 
figured. 
Parreysia regis, new species 
Plate XX XI, Figures 12-126 
Lake Edward at Kabare (J. Bequaert Coll.). 
The shell is oblong, moderately convex; the dorsal and ventral margins sub- 
parallel, both slightly curved; covered with a thin, glossy, olive-brown epidermis. 
About a third of the width is finely zigzag ridged; at the beaks the apices of the V- 
shaped corrugations are emphasized, forming two radial series of tubercles. 
