president's address — SECTION D. 97 



representative in the Australasian region of a genus which is 

 elsewhere found in South America and Cuba. 



Planorbis has 5 peculiar species, but the genus is not repre- 

 sented in Victoria, being recorded however from New South 

 Wales, South Australia and Queensland. 



Segmentina is absent in Tasmania and has only 2 species 

 in Australia, one confined to Victoria and one to New South 

 Wales. 



The genus Melania, as before said, is most strongly 

 developed in the northern parts of the Continent, Queensland 

 having 10 species, New South Wales 3 and Victoria and 

 South Australia only 1 each. It appears to be quite absent 

 from both Western Australia and Tasmania, the one species 

 which spreads far south (M. balonnensis ) being common to 

 Queensland, New South Wales, Victoria and South Aus- 

 tralia. 



Paludina again is a genus scarcely found save in the 

 northern parts and is wanting both in Victoria and Tas- 

 mania. 



In the Rissoidae the genus Bithynia has 7 species all 

 peculiar whilst Victoria and New South Wales have only 

 one each. Amnicola again has 7 peculiar species and is not 

 represented on the Continent. 



The family As&iminidae is of interest inasmuch as the genus 

 Assimineais represented in Tasmania, Western Australia and 

 Queensland and again in New Zealand whilst it is also found 

 in Europe, India, and Polynesia. 



In the Lamellibranchs 4 out of 5 genera found in the 

 Australian region have representatives in Tasmania. These 

 are — Sphairiura, with one peculiar species ; Pisidium with 2 

 peculiar species ; and lastly Unio. The species of this genus 

 which have been described are not altogether satisfactory and 

 at present Tasmania may be credited with one, Unio moretonicus, 

 which is probably a variety of U. australis and common to 

 Tasmania and Australia. 



The fifth genus Mycetopus is only recorded from Northern 

 Australia where it has one species f3I. rugatus)^ and of this 

 Edgar Smith points out that, " It is remarkable that Aus- 

 traha and South America should possess species so much alike 

 as M. siliquosus" and the North Australian form. 



In contrast with the community of land shells existing 

 between Tasmania and Victoria, it is important to notice the 

 marked absence relatively of such a community in freshwater 

 forms. Out of more than 50 species in Tasmania only 4 



