ANCIENT LAND CONNECTIONS 



411 



the members of this genus is their astonishing resemblance, 

 as mentioned before, to certain species of the European group 

 Helicigona, including the well-known Arianta arbustorum. 

 Some of the American shells are externally so much like the 

 latter that they were placed into the same genus until recently. 

 Dr. Pilsbry,* however, maintains that the European Heli- 

 cigona differ anatomically from Epiphragmophora, and that 

 the two should be placed in quite distinct groups. Even on 

 anatomical grounds opinions may differ very radically, for 

 Dr. von Ihering claims that the American Epiphragmophora 

 and the members of the group Helicigona are genetically con- 

 nected. After careful examinations of the European Arianta 

 arbustorum and the Argentine Epiphragmophora tucuma- 

 nensis he could perceive no noteworthy anatomical difference 

 between the two, and placed them both into the same genus. 

 If Dr. von Ihering's f observations are correct, this is another 

 example of the same extraordinary relationship between Euro- 

 pean and west American forms that I have had occasion to 

 point out in previous chapters. Occasionally this relation- 

 ship manifests itself only in Europe and south-western North 

 America. In other cases it exists simply between European 

 and western South American forms. In this case both the 

 American western centres are related to the European centre 

 of dispersal. It clearly illustrates, as stated before, that 

 Europe was once joined to a mid-Atlantic land bridge which 

 communicated directly with a belt of land lying to the west of 

 America. On the disappearance of the latter many of the 

 animals inhabiting that belt of land took refuge in the western 

 parts of America and still persist there. 



Epiphragmophora, all the same, does not clearly reveal the 

 special affinity that exists among the older forms of animal 

 life of south-western North America and southern South 

 America. The wingless insects known as " bristle tails "(Thy- 

 sanura) are generally looked upon as a very ancient group. 

 Among these the genus Japyx, which is easily recognisable 

 by its forceps-like tail-appendage, has a noteworthy distribu- 

 tion. Japyx solifugus occurs in the Mediterranean region, 



* Pilsbry, H. A., " Manual of Conchology (Pulmonata)," IX., p. 195. 

 f Ihering, H. von, " System der Heliciden," p. 422. 



