14 OEIGIN OF LIFE IN AMEEICA 



Professor E. Morse first discovered the shell of this snail 

 among the contents of ancient " kitchen-middens," those 

 peculiar refuse heaps of primitive man, on some of the islands 

 off the east coast of Maine. He pondered over this singular 

 mystery and finally came to the conclusion that the snail must 

 have slowly wandered, during a long series of centuries, from 

 the Old World to the New, by means of an ancient North 

 Atlantic land bridge. Mr. Johnson,* to whose instructive 

 paper I am indebted for this information, states that Dr. 

 Binney and Professor Cockerell concurred in Professor 

 Morse's opinion. He also informs us that the Eev. Winkley 

 and he were of opinion that the arrival of the snail Helix 

 hortensis in America must have taken place before the advent 

 of the Glacial Epoch. 



This theory, as can be imagined, was by no means gene- 

 rally accepted in America. All doubts, however, as to 

 the claim of Helix hortensis being an indigenous American 

 species are now set at rest, through the discovery by 

 Dr. Dall f of the shell of this snail in undoubtedly Pleisto- 

 cene deposits in the State of Maine. Some naturalists might 

 still be inclined to urge that greater facilities for occasional 

 transport across the Atlantic may have existed in those remote 

 times than at present, and that the argument in support of 

 a land hridge is not convincing. No evidence, however, in 

 favour of an ocean current from Europe to North America in 

 Pleistocene times has as yet been brought forward, while the 

 conviction in the former presence of a land connection between 

 north-eastern America and north-western Europe is based 

 upon other biological observations. From a geological point 

 of view we can scarcely hope to he able to determine the period 

 or periods during which this land bridge existed. The bathy- 

 metrical features of the north Atlantic, according to Pro- 

 fessor Hull,$ Dr. Spencer § and Dr. Nansen,|| point to a pre- 

 Glacial elevation of the land in northern latitudes. Dr. 



* Johnson, 0. W., " Distribution of Helix hortensis," p. 73. 



t Dall, W. H., "Land and Freshwater MoUusks of Alaska," p. 20. 



J Hull, E., "Submerged Terraces and fiiver Valleys." 



§ Spencer, J. W., " Submarine Valleys," p. 224. 



II Nansen, F,, "North Polar Expedition," p. 192. 



