1S6 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



gather from the paper referred to. Mons. Fischer's conclusions 

 are that the genera Hydrohia and Paludestrina are synonymons, 

 including marine and fluviatile shells, but as Hartmann only 

 employed the term for marine shells, the name should be confined 

 to them. 2. That Paludinella and Assiminea are synonymons. 

 8. Amnicola is probably a genus peculiar to America. 4 The 

 little fluviatile species of Paludina with spiral opercula, should be 

 arranged under the genus Bythinella, which is the only genus 

 specially erected for them. 5. The marine species should be 

 called Littorinella. 6. Mons. Fischer doubts however if the 

 marine and fluviatile forms are generically distinct. Any further 

 remarks on the subject are contained in my paper read before the 

 Royal Society Tasmania. I merely state that I adopt the con- 

 clusions of Mons. P. Fischer. 



Genus Bythinella, Moquin Tandon, 1855. 

 Bythinella coralla, Gould {Melanta*), Boston Soo. Nat. Hist., 

 vol. 2, p. 4 " This," says V. Martens, " is a very variable shell, 

 sometimes with spines and sometimes destitute of them." Some of 

 the figures of the species from the difierent authors who have 

 given it different names, vary very much, yet I have no doubt 

 that the shell is in every case the same as that which is represented 

 on the accompanying plate ; and I have but little doubt also that 

 these forms are specifically identical with others under different 

 names which are found in Australia and Tasmania. At least I 

 cannot point out any single feature upon which I could rely for 

 their distinction. Under these circumstances, it will serve no 

 useful purpose to multiply names any more than to say that those 

 shown on plate 13, figs. 2, 3, 5, are what I distinguish as variety a. 

 and b. The differences between this shell and B. Wisemanimia, 

 Braz., are that the spines are always distinct on the New 

 Zealand shell, but they often merge into a keel on the species 

 named. I think also the latter is a less turriculate and more 

 turbinate form. The absence of these spines or keel from some 

 of the specimens, is I imagine, wholly attributable to the fact that 

 these features result from a periostraca which readily disappears. 



• Either Reeve's figure of the shell is incorrect or the species must be different as the 

 poristome is not continuous. 



