73 



ToucMng the specific alliances of the Victorian terrestrial 

 mollusca, we are at once arrested by the fact that only about 

 one-half of the total number of species are endemic, and of 

 these two, at least, are so closely related to Tasmanian species 

 that had they been found living in the same geographical 

 region they would have been regarded as not more than varietal 

 forms. Of the eitra-limital species, seven occur in Tasmania, 

 and there is a slight community with South Australia and with 

 New South "Wales. The geographical range of the Victorian 

 species is set forth in Appendix I. 



That there should be some specific points of contact between 

 the mollusean fauna of Victoria and Tasmania is not sur- 

 prising ; but that there should be so large a proportion in 

 common is most startling. Thanks to Mr. Petterd, I have had 

 the means of comparing Tasmanian and Victorian examples of 

 all the species in common, and after a most rigid examination 

 I am forced to acknowledge the specific identity of seven. 

 Mr. Petterd considers also Helix ruga and H. Allporti to have 

 place in the same category ; but as the Victorian examples 

 show differential characters, I have regarded them as distinct 

 species. It is true that the differences are so very trivial that 

 but for the fact of the shells exhibiting them are found so 

 isolated from their congeners, one would not be justified in 

 separating them. If the other extreme view be adopted, then 

 there are nine species, out of a total of 23, in common between 

 Victoria and Tasmania. 



Referring again to the table giving the number of species 

 inhabiting Victoria and its neighbouring colonies, we may well 

 ask, why this paucity of species? It certainly cannot be 

 attributed to climatic conditions, as South Australia, with its 

 drier climate, possesses about 50 species, many of which 

 inhabit regions subjected to continued droughts and scorching 

 heats ; whilst Tasmania, which is paralleled with the alpine 

 regions of A'ictoria, counts 73, and has, moreover, a rich and 

 varied group of aquatic pulmonate snails. I would fain seek a 

 cause in recent geological changes. It is popularly held, but I 

 think erroneously, that Australia is an ancient continent. 

 But the present configuration of the surface of Victoria is 

 largely due to forces which have exerted their influence over 

 vast areas, and at comparatively recent times. A glance at a 

 geological map of the colony will satisfy you that the larger 

 portion of it, on the south of the main watershed, is covered 

 with igneous rock ; and a personal examination would result in 

 the opinion that much of the remainder had been similarly 

 mantled over, from which it has been stripped in later years. 

 IS'ow, the period, at which this vast sheet of basalt and porphy- 



