1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 13 
i . : 
Brief definitions of the genera and higher groups, original or adapted, 
and figures of most species in our possession have been given to make the 
work useful to traveller-naturalists and to other interested students who 
may be stationed in the Belgian Congo out of reach of scientific libraries. 
Since practically all publications upon fresh-water mollusks of the 
Ethiopian Region had to be consulted in the course of our work, we have 
added a reference list of the species of this region to our discussion of the 
material in hand. Experience has shown the need of such a list eee 
fact, something of the sort must be compiled by anyone working systema- 
tically on the fauna.!’ In so wide a field as that of African conchological 
literature it may be expected that we have overlooked some hidden 
species, or even missed one in the open, but it is hoped that our round-up 
will be found reasonably complete. ya 
While the fauna of northwestern Africa was not considered in the 
course of our work, many of the forms described from Lower Egypt were 
listed, especially in the typically Ethiopian genera; but no claim to 
completeness is made for that region. As a rule we have given only the 
localities mentioned in connection with the original descriptions, since 
it is frequently impossible to judge of the correctness of subsequent 
identifications without a study of the material on which they were based. 
It will be noticed too that we have not always accepted the synonymies 
proposed by previous writers: in many cases these may have been cor- 
rect, but frequently they were made without examination of original 
_ or topotypic material. | 
The authors desire to express their great indebtness to Professor 
‘Henry Fairfield Osborn, President of the American Museum, for the keen 
interest he has taken in this work. His continuous encouragement and 
generous support have rendered possible the completion of this report 
and its early publication. In form, it has been designed for incorporation 
as a part of The Zodlogy of The Belgiam Congo, the series planned by 
President Osborn on the scientific results of the American Museum Congo 
Expedition. 
For the privilege of studying these extensive collections and for 
‘generous assistance extended during the course of our work, we are 
grateful to Dr. F. A. Lucas, Honorary Director of the American Museum, 
and Dr. Roy W. Miner, Curator of Lower Invertebrates. 
As in the past, Mr. Herbert Lang, leader of the Congo Expedition, 
has unreservedly placed at our disposal all possible information and help. 
owe It, 1909, Abh. Senckenberg. Naturf. Ges., XX XIII, pp. 53-97, has listed the mollusks of the 
Wibispee tee but without arene or localities. His list is therefore of little practical use; more- 
over, it is marred by many omissions and inaccuracies. 
