The relationship between the palaearctic and nearctic faunas 



235 



FIG. 29. Distribution of Cepaea {Helix) 

 hortensis O. F. Miill. — Open circles = 

 doubtful or accidental occurrence. 



(According to Johnson, 1906, Taylor, 191 i, 



0KLAND, 1925, 1927, PiLSBRY, 1939, &C.) 



(From PiLSBRY, 1939.) 



p. 105) regarded the distribution of Cepaea hortensis as one of the strongest zoo- 

 geographical facts in favour of his theory of continental drift {vide below, p. 284). 



It seems to me that the solution of the enigma "introduced contra native" in the 

 case of Cepaea hortensis in North America stands and falls with the dating of the 

 subfossil remains in Maine and Nova Scotia quoted above. The only published 

 statement possibly allowing this, as far as I know, is the observation that in Penob- 

 scot Bay the shells were found associated with bones of an extinct species of mink. 

 This has apparently impressed subsequent students of the question with the assumed 

 high age of the Cepaea. The known history of Mustela macrodon Prentiss., however, 

 is very disappointing in this respect (Anderson, 1946, p. 192-193):— "According to 

 Hardy the animal became extinct in Maine about the year i860. Traditionally 

 said to have been commonly trapped along the coast of the Bay of Fundy in southern 

 New Brunswick, — ". Until further, reliably dated subfossils of Cepaea hortensis 

 are discovered, nothing seems to prevent those hitherto found being of "post- 

 Columbian" age. 



