DISTRIBUTION OP PUPILLIDAE. 141 



areas on tlie map being more or less dubious, Pupilla proper 

 has not spread far to the south, but the earlier subgenus 

 Gibhulinopsis^ has reached South Africa, Australia and 

 Tasmania. The subgenus Striopiipilla in western North 

 America must be due to a much earlier migration than that 

 of Pupilla s. str. 



Fig. 5, the northern group of Gastrocopta, has about the 

 same range as Pupilla, but it is still present in many islands 

 between Asia and Australia, and it has been differentiated into 

 several regional subgenera in its secondary areas. North 

 America and Australia. 



Fig. 8, the routes of dispersal of the typical group of Gas- 

 trocopta are problematic. The rather high stage of evolution 

 shown by the complete concrescence of angular and parietal 

 lamellae, and the great similarity of American and Ethiopian 

 species are points in favor of recent evolution and dispersal 

 of the stock; but on the other hand, its distribution in the 

 tropics of both hemispheres, and tiie presence of strongly 

 differentiated derivatives, such as Immersidens, Chaenaxis 

 and probably Gihhulina, argue for considerable antiquity. It 

 may be a genus which matured early in the Ethiopian Region 

 and reached America via a transatlantic land bridge, but this 

 would put it back into the Cretaceous or at least Paleocene, 

 with practically no change in part of the stock since. Further 

 paleontologic discoveries must be awaited before deciding be- 

 tween an Atlantic or the northern route ; but in any case, the 

 extreme similarity of African and American species is 

 remarkable. 



The very extensive distribution of some species of Gastro- 

 copta due to commerce is not represented on the maps. 



Fig. 6, Pupoides has much in common with Gastrocopta 

 s. str. in distributional peculiarities, but unlike that group, 

 Pupoides reached Australia. The problem of dispersal is the 

 same in both genera. The presence of Microstele in European 

 Miocene and apparently in Chinese Pliocene is interesting in 

 this connection, as this genus appears to stand in an ancestral 



1 This is a prior name for Primipupilla; see vol. 27, p. 254. 



