1926] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 357 
According to E. A. Smith, who had before him the types of E. 
parasvteca (Deshayes) and author’s specimens of E. ferruginea, the former 
“is slightly longer and narrower and the concentric striz are stronger 
and more lamellar” than in E. ferruginea. Unfortunately, the dimen- 
sions of the type of parasitica have not been published. Jickeli’s meas- 
urements and figures show the relation of diameter to length to be 
about the same as in ferruginea in some examples, in others the diameter 
is half the length. Whether ferruginea, parasitica, and letourneuxi are 
really distinct remains still rather doubtful; but the Congo form seems 
to differ constantly by its relatively greater diameter. 
Eupera mediafricana etheriarum, new subspecies 
Text Figure 80 6, c, d 
Dungu River at Faradje (H. Lang Coll.; December, 1912). 
The shell is trapezoidal, broad (the height about 78 per cent of the length), 
rather plump (the diameter about 58 per cent of the length), fragile, uniform buff 
when the thick coating of iron hydroxid is removed, irregularly striate, the striz 
bearing irregular epidermal lamin, much closer than in mediafricana of the same size. 
The beaks are rather prominent, at the anterior two-ninths of the length. The 
anterior end is much smaller than the posterior, rounded; posterior end straightened 
and sloping back of the hinge, rounded below; basal margin gently curved. 
Length, 3.45 mm.; height, 2.7 mm.; diameter, 2 mm. 
Fig. 80. a, Eupera mediafricana Pilsbry and Bequaert, Stanleyville. b-d, 
Eupera mediafricana etheriarum Pilsbry and Bequaert, Faradje. | 
