70 



A Census of the Mollusgan Fauna of 

 Australia. 



By Professor Ralph Tate, F.L.S., F.G.S. 



[Read October 2nd, 1888.] 



My object is, in this essay, to present a comprehensive view of 

 the constituents of the molluscan fauna of South Australia 

 (omitting Polyzoa), and to indicate their exoteric relationships. 



The accompanying tables are based upon a list of species 

 showing their occurrences by political boundaries, which I have 

 been compiling for the past ten years, partly as the result of bye- 

 work in connection with the distribution of the genera in the 

 Australian Tertiary deposits. This list cannot be without faults, 

 but I think it makes a fair approach to accuracy both as to 

 specific identities and distribution. I fear, however, that the 

 number of species is in excess, as some of our Australian workers 

 have relied too much on geographical isolation as an index to 

 specific distinction ; still, the duplication cannot be very serious 

 as to affect the general conclusions at which I have arrived and 

 submitted herein. 



It is admitted that terrestrial provinces are not necessarily 

 co-ordinate with marine ones, and it is the more desirable to 

 review them independently, inasmuch as the terrestrial and 

 fluviatile species of Australia are exclusively endemic, if we 

 except a few species of Melaiiia and Neritina. 



The Marine Molluscan Fauna of Australia. 

 The marine fauna admits of grouping into two sections — one 

 occupying the tropical shores, and largely consisting of migrants 

 from the Oriental Marine Province ; and the other belonging to 

 the temperate waters, and largely consisting of endemic species 

 and possessing several restricted genera. Where to draw lines 

 of demarcation between the two regions is a difliculty, as no 

 actual barriers to migration occur ; on the east the transition is 

 more pronounced than on the west coast, and I select the latitude 

 of Maryborough, coinciding with the southerly termination of 

 the Great Barrier Reef as a convenient point of separation. On 

 the west coast a tropical fauna prevails as far south as Shark 

 Bay, whilst at Freemantle the Australian species are in an 

 ascendancy ; no extensive lists of species have been published 

 from any one locality north of King George's Sound, so that I 



