96 OBSERVATIONS ON THE VARIABILITY OF THE TASMANIAN UNIO. 



various parts of Australia may ultimately prove to be local 

 varieties, or particular stages of growth of one widely 

 distributed species. Indeed, any of those named have already 

 been linked together in the verv interesting communications 

 contributed by Edgar A. Smith, F.Z.S. (^), Prof. Tait and 

 J. Brazier, F.Z.S. (*). For these reasons I, at least, am 

 disinclined to accept a fresh synonym for the Tasmanian 

 variable form. Among the individuals which prevail locally, 

 of course, it would be easy to select some one or two types 

 which would slightly differ in size and form with any one 

 type-figure of allied Australian forms, but such a proceeding 

 would be very misleading when we regard the extreme 

 variability of our local example. As an illustration of what 

 might be done in this way, I may observe that the manner in. 

 which the umboes of the shell are eroded by carbonic acid, 

 often produces malformation or some considerable modification 

 in the form of adult specimens. 



This is conspicuously the case with one of the specimens 

 figured (No. ) ; and it is also remarkable that in this same 

 specimen the animal has almost completely absorbed the 

 primary teeth in both valves, while the lateral teeth have 

 been partly absorbed towards their extremities. 



Under these circumstances it is apparent that a satisfactory 

 classification of the Unionidce of Australia cannot be 

 established until the various stages of growth, and the 

 individual variability of the forms of each Australian habitat 

 have been properly studied. The observations made in this 

 paper, together with the accompanying figures of Tasmanian 

 forms, will, I hoj^e, be of some help in this direction. 



1 On the Fresh Wiiter Shells of Australia (Journ. Lin. Hoc, April, 1S82). 



2 Check Li.st of the Fresh Water Shells of Australia (Pro. Lin. Soc. N.S. Wales, 

 May, isal). 



