BY K. M. JOHNSTON, F.L.S. 87 



perhaps, of Mr. Woods and Mr. Petterd, the naturalists at a 

 distance from Tasmania, who described the first four or five 

 forms, had no other characters at their command than the 

 shell afforded. 



I merely make these observations in justice to myself, 

 "because Mr. Petterd in his otherwise excellent paper* road 

 this evening, has remarked that hitherto " unfortunately 

 almost all our writers have simply devoted their attention to 

 the outline of the shell and structure of the operculum, few, 

 if any, devoting the amount of attention to the malcological 

 characters that the more modern and elaborate system of 

 classification demands." 



I think Mr. Petterd is somewhat unjust as well as inac- 

 curate in making this statement without further qualification. 

 So far as local observers are concerned, it is true, neither 

 himself, in the description of the two fresh water forms, viz., 

 GundalacJiia Beddomei aTiHAficyliis Irviniic, published by him, 

 nor Mr. Woods in the first and most important of all con- 

 tributions to our knowledge of Tasmauiau fresh water shells, 

 give any description of the animals other than those relating 

 to the exo-skeleton, and the operculum where present; but it 

 is not true so far as I am concerned, as the statement I have 

 already made proves. 



As some confusion has already occurred, owing to the 

 alterations in nomenclature more recently made, I have 

 thought it desirable to draw up a tabular historical list 

 showing the various modifications and additions which have 

 been made in connection with Tasmauiau fresh water shells 

 since Mr. Woods' paper was published in 1875. 



Classification. 



The classification of the various forms of Lvmnreidae and 

 Hydrobiinae presents many difliculties, and these already 

 have been the principal cause of the present overload of 

 synonyms, which must be a fruitful source of error to many. 

 The confusion now existing will not be dissipated by the 

 mere creation of fresh names for genera. Already, owing to 

 the various modes of classification adopted by independent 

 authors, the sub-family /([j''^'''"^^''"'<^ is broken up into an iutoi'- 

 minable number of genera, each with a host of synonyms, 

 while the characters of many of them do not justify their 

 separation from each other. 



Certain genera are based upon the form and character of 

 the shell and its operculum. Others are established upon 

 the form of the luu/zle and teutacuke of the animal, while 

 not a few are erected upon the character of the odontophore 

 and its denticulce. So long as there are different methods 



* Contributions f(ir a Systematic Catalogue of the Aquatic Shells of Tasmani;u 



