2 88 POPULAR SCIENCE MONTHLY. 



The Helices of the West Indies lend no aid to those who advocate 

 the hypothesis of an 'Atlantis' bridging or partially bridging the 

 Atlantic, for they are not allied to species of Madeira, the Azores, Cape 

 Verde or Canary Islands. Their anatomy is vastly nearer Mexican, 

 Californian and East Asiatic groups. 



N"o generalization based upon the distribution of snails, or of any 

 one group of animals, can be satisfactory unless it is supported by the 

 evidence of animals of other groups, and by that of plants. In extend- 

 ing the data relative to the zoogeography of America and Asia, it may 

 be said that the evidence of the naked snails or slugs fully supports 

 that of the Helices. The West American slugs have their cousins in 

 China and the Himalayas, not in eastern Xorth America. The fresh- 

 water crayfish of our Pacific slope belong to the Old World genus 

 Astacus, not to the East American genus Canibarus. The evidence of 

 fishes seems to strongly favor a former connection of Asia and 

 America. Thus. Gunther* deduces a Central Asian origin for the 





'^^^'r 



Dart-Bearing Helices. Upper Figures Two Species of Eulota from Japan; Lower 

 Figures Epiphragmophora fAom California. 



Cyprinoids, or Carp family, which is also very numerously represented 

 in America. Moreover, he regards the Chinese species of Catostomus, 

 or 'sucker,' as a return emigrant from America to Asia. The North 

 American catfishes belong to an East Asian group of the family; and 

 our garpike has a representative in Chinese waters. 



Such evidence as the higher vertebrates afford do not strengthen 

 the case stated for the snails, because their evolution has been vastly 

 more recent and rapid, and their means of distribution are far less 

 restricted. Thus the horses have attained their present distribution 

 since the Pliocene, but they are capable of spreading rapidly wherever 



* The Study of Fishes, p. 244. 



