THE NAUTILUS. 103 
the evolutionary process has been active during the latest geo- 
logical periods. While the Belgian Congo has of course been 
only very imperfectly explored for land mollusks, about 500 
localities are represented, and about 390 species and races have 
been found. Of these 390 forms, I find 214 reported from one 
locality only. The case is even stronger than these figures sug- 
gest, as when two or more localities are given, they are often 
only short distances apart, or perhaps in some cases different 
names for essentially the same place. Again, of 214 species and 
subspecies in the collection reported on, 160 required new spe- 
cific, racial or varietal names. When we consider the amount 
of specific and racial diversity thus indicated, making full allow- 
ances for our imperfect knowledge of the distribution of the re- 
corded species, it becomes evident that the total existing fauna 
must amount to some thousands at least. 
It is well known that the high mountains of tropical Africa 
are inhabited by certain organisms, especially plants, very 
closely related to Palearctic species. In the case of the plants, 
at least, it is possible that the seeds were brought by birds. 
Among the mollusks, it is interesting to find a Vitrina high up 
on Mt. Ruwenzori, near the line of perpetual snow. But after 
all this is not a typical Vitrina ; it differs in the less extensive 
mantle, the sculpture of the shell, and in the teeth. Dr. Pils- 
bry accordingly establishes for it a subgenus Calidivitrina,—the 
name rather unfortunately chosen, since it is not an inhabitant 
of the hot lowlands. On comparing the Congo mollusks with 
those of tropical Asia, some puzzling questions arise. Thus 
among the slugs there are such similarities that Godwin-Austen 
formerly placed both African and Indian species in his genus 
Africarion. He now agrees that the Indian slugs constitute a 
quite distinct genus ( Pseudaustonia), and it seems at least prob- 
able that the Indian series has undergone an evolution similar 
to, but quite independent of, the African. These conclusions 
could never have been reached without a study of the soft an- 
atomy, and thus we are led to treat with some caution those 
cases of similarity among the smaller shells, the anatomy being 
unknown. There is, for example, a striking resemblance be- 
tween some of the African and Oriental species of the Gulella 
