SciiAKFF — Former Land-Bridge between N. Europe and N. America. 19 



A western species iu Europe, Helix hortcnsis, is remarkable for its exten- 

 sive nortliom range. It occurs in Scandinavia, all over the British islands, 

 in the Shetlauds and Faroes, and even in Iceland (fig. 4). It is 

 altogether absent from Asia. Its occurrence in southern Greenland had 

 generally been attributed to a recent human introduction ; but it has been 

 taken in several different localities ; and we must, I think, look upon it as 

 an indigenous species. Its presence in the state of Maine in North America 

 has frequently been cited as a familiar example of the facility with wliich 

 European species are introduced by human agency to foreign countries. 



Fig. ■!. — Map indicating tlie geographical distribution of ll.e t^nail ITcli.r hortenaia. 



Until the year 1864 no other theory was ever thought of. During that year, 

 however, Professor E. S. Morse first discovered the shell of this snail among 

 ancient "kitchen- middens " on some of the islands off the coast of Maine. 

 This fact led liim to reconsider the generally accepted view of its being a 

 recent introduction. It seemed to him much more likely that the snail had 

 wandered along some ancient coast-line from the Old World across the 

 North Atlantic. Dr. Binnoy, and more recently Professor Cockerell, 



