XI 



QUESTION OF A NEANTARCTIC CONTINENT 



359 



which the Mollusca may offer evidence. Von Ihering holds that 

 an essential difference can be observed between certain of the 

 Uniouidae which inhabit S. America, Africa, and Australia with 

 New Zealand, and those which inhabit Europe, Asia, and N. 

 America, but the point can hardly be regarded as definitely 

 established at present. Something perhaps may be made of the 

 distribution of Bulimus and Bulimulus. It seems difficult to 

 explain the occurrence of sub-fossil Bulimus on St. Helena except 

 on some such lines as have been recently adduced to account for 

 the presence of struthious birds in the Mascarenes, and possibly 

 the form Livinhacea may be a trace of the same element in S. 

 Africa. Again, the Liparus of S. and W. Australia, with the 

 Caryodes of Tasmania, and the Leucotaenia and Clavator of Mada- 

 gascar (which all may be related to Bulimus'), together with the 

 Placostylus of New Caledonia and the adjacent islands, reaching 



Fig. 237 . — Macrocyclis 

 laxata Fer., Chili. 



even to New Zealand, and perhaps even the Amphidromus of 

 Malaysia (which are more akin to Bulimulus), may be thought 

 to exhibit, in some remote degree, traces of a common ancestry. 

 The land operculates give no help, and, of the carnivorous 

 genera, Rhytida is a marked link between Africa and Australia, 

 while Streptaxis is equally so between S. America and Africa. 

 As regards fresh-water Gasteropoda, Ampullaria is common to S. 

 America and Africa, while Isidora is common to Africa, Australia, 

 and New Zealand, but is altogether absent from S. America. 

 Gundlachia occurs in Florida, Trinidad, and Tasmania, but has 

 not been detected in Africa. It must be concluded, therefore, 

 that the present state of the evidence which the Mollusca can 

 afford, while exhibiting certain curious points of relationship 

 between the three regions in question, is insufficient to warrant 

 any decided conclusion. 



