102 THE NAUTILUS. 
THE LAND MOLLUSKS OF THE BELGIAN CONGO.* 
BY T. D. A. COCKERELL. 
The American Museum of Natural History has issued a series 
of reports on its Congo Expedition, all characterized by fullness 
of treatment and abundant and beautiful illustrations. Other 
similar reports are in course of preparation. The completed 
series will constitute a guide to the zoology of equatorial Africa, 
full of interest for the general naturalist and evolutionist, as 
well as for specialists in the several departments. Among these 
reports one of the most interesting is that on the Land Mol- 
lusks, by Dr. Pilsbry. The presentation of the subject is so 
clear and complete, and the illustrations are so good, that the 
reader has no difficulty in understanding the characters of the 
fauna, though he may have known very little about it before. 
To one accustomed to the mollusks of America or Europe, the 
tropical African series seems to belong to another world. Even 
when there is a certain similarity of form, as among the Heli- 
cide, the anatomy shows that we are dealing with strange generic 
types. The closest affinity is of course with the fauna of the 
Oriental region, yet even that is remote, although some doubt- 
less very ancient genera range through tropical Asia and Africa. 
There is here a rather close parallel between the distribution of 
the land mollusks and the fresh-water fishes. Certain genera 
of fishes, but with distinct species, occur in the fresh waters of 
India and of tropical Africa, but the latter region has many re- 
markable types of its own, in some cases much more allied to 
neotropical genera than to anything in India. It is evident 
that Africa, the land of the okapi and the tsetse fly, is a store- 
house of ancient groups of animals, some of which at least, were 
formerly much more widely spread. While we thus emphasize 
the probable antiquity of various African groups or genera, we 
find remarkable specific diversity, apparently indicating that 
* Henry A. Pilsbry. A Review of the Land Mollusks of the Belgian Congo, 
chiefly based on the collections of the American Museum Congo Expedition, 
1909-1915. Bulletin American Mnseum of Natural History, Vol. XL, p. 
370, 23 plates (8 colored), 1919. 
