244 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



Risella Bruni, Crosse, Jour, de Conchy., 18G4, p. 239. 



Hab. Spencer's Gulf, South Australia. 



Risella livlda, Philippi, Adams. 



Bah.— 1 



Risella vittata, Philippi, Adams. 



Hab. Adelaide (?). 



Risella imbricata, Cray, Philippi, Adams. 



H a b.—l 



From this list I think we may at once erase the three last. 

 From the definition given by the authors of the specific names, we 

 may be quite sure that we are dealing with mere varieties, or 

 young individuals of the three first species named. Having paid 

 attention to this genus for some years, and having examined some 

 hundreds, nay, I may say thousands of specimens from all the 

 Australian colonies as well as Tasmania, T may safely say that 

 there are no such species as R. imbricata, viatata, and livida, but 

 that individual specimens of A*, nana may easily be found to cor- 

 respond with all of them. 



It is with some considerable hesitation that I say that I think 

 Mons. Crosse's species, It. liruni, should also be reduced to a mere 

 local variety of R. nana. I should say it is no more than a pale 

 and rather more tumid species inhabiting Spencer's Gulf. 



This leaves us five species which must again be reduced, because 

 R. aurata is only the male animal of R. nana. This may appear 

 startling, but it is a fact which I have established after long-con- 

 tinued observation. In the first place, the two animals may be 

 seen breeding together any day upon the rocks of D'Entrecasteaux 

 Channel at low tide. If, moreover, the two species are kept in a 

 small aquarium, they will breed readily, and R. nana will be the 

 mother of the fry. 



My observations here, however, revealed a still more surprising 

 fact. Having ascertained beyond a doubt that both male and 

 female shells (as for convenience we may call them, though some 

 other term is required to express the sexual relations) are herma- 

 phrodite, if R. nana (female) and R. aurata (male) are kept 

 apart in separate glass jars, they are seen to couple together, that 



