256 MR. E. A. SMITH OJT THE 



Ancylus, Physopsis, Mycetopus, and NaviceUa have but single 

 representatives. 



The great uncertainty and difficulty in determining the limits 

 of most freshwater shells is well known. On this account, and 

 considering the insufficient amount of material to work with, I 

 trust that great allowance will be made for those errors which 

 undoubtedly exist in the following account. However, I am con- 

 fident that my labour has not altogether been expended in vain ; 

 for to bring together a list of the known species and to correct 

 and amplify some of the descriptions will, it is hoped, be of some 

 use to those who may hereafter study this particular group, and 

 have not access to the types preserved in the British Museum. 



In conclusion, I have to thank, on behalf of that institution, 

 Mr. John Brazier of Sydney, who some time ago presented a large 

 series of shells from the Australian rivers, especially valuable, as 

 to each specimen its particular locality is attached. 



To Mr. Taylor, editor of the 'Journal of Conchology,' my 

 thanks are also due for the loan of another set, including three 

 species of FJiysa, described in that publication by himself and 

 Mr. Nelson. 



I should also state that I have not included in this account the 

 freshwater shells of Tasmania, as this subject has been investi- 

 gated by more competent naturalists resident in that island. 

 Mr. Tenison-Woodp, Mr. Johnston, Mr. Brazier, Mr. Petterd, 

 and others have written many valuable contributions to the 

 knowledge of that subject. Considering the ease with which the 

 ova of most species can be carried from place to place, it is very 

 probable that some of the Tasmanian species will hereafter be 

 proved to be the same as others from the mainland ; and this is 

 a subject to which I call the attention of Australian concho- 

 logists. 



Grenus Melania. 



1. Melania amaetjla, Linn. 



Sab. Amboina (RumpK) -. Sumatra, JFiji Islands, Solomon 

 Islands, Mauritius, Madagascar, JSTicobar Islands, &c. {Brit. 

 Mus.) : Saltwater Creek, Cardwell, Eockinghara Bay, Queens- 

 land {Brazier and Becldome). 



Mr. Beddome remarks that the creek is always freshwater 

 where these are found. 



The specimens from Australia have the form of the variety 



