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 Palsearctic 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 (falidivitrina, 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 



