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It may be as well if I give, in tlie very words of Mons. 

 Fischer, wliat he says of some of tlie synonymous genera : — 

 " (Litorinella, Brann, 1842.). Braun proxDosed this new genns; 

 for PaluclUm with spiral opercula. In 1845 Thoma applied 

 the name Littorinella to the Cyclostoina acutum of Draparnand 

 (Jahrhuch des Vereins filr Naturhunde in Herzogtliicme Nassau^ 

 Heft. 2, p. 125). We must conclude that Littorinella ought 

 to be reserved for marme or brackish water shells. The 

 genus Paludinella was erected in 1841 by PfeifPer (Wiegm. 

 Arch. 1, ]). 227) for the Helix littorina of Delle Chiaje — a 

 marine species regarded as a Truncatella by Philippi, and 

 placed in the genus Assiminea by all modern naturalists. 

 Relying on the marine habitat of Pfeiffer's type, Lovcn, in 

 184*6, placed Pennant's Turbo ulvce amongst Paludinella ; but 

 it is difficult to explain why, quite recently, Frauenfeld, Kreg- 

 linger, Kobelt, Paladilhe, &c., have distinguished all the 

 little fiuviatile Palitdinas by the name of Paludinella. It is 

 one of the most astounding blunders in nomenclature, and 

 proves how persistently one author follows another without 

 the least examination. The genus Amnicola of Gould and 

 Haldeman (Supplement to a Monograph of the Lhnniada;, p. 3. 

 1849) is defined thus : — Head proboscidiform, shell like 

 Paludina, operculum corneous and subspiral. No species is 

 named as a type, but it is certain that the authors had in 

 view only fiuviatile species. Ultimately Groiild, in the Inver- 

 tehrata of Massachusetts, characterised the genus with more 

 detail, and took for a type Paludince with few whorls. Stimp- 

 son (On Hydrohia, 1865, p. 13) gives a figure of the oper- 

 culum of Amnicola, and attributes to it a peculiar structure 

 which is not fomid in pretended Amnicola of the old world. 

 I consider, therefore, that the genus Amnicola should be 

 restricted to American species. Frauenfeld has adopted a 

 very arbitrary mode of distinguishing the genus all over the 

 world, i.e., the globular form and short spire. Bythinella is 

 a genus erected by Moquin-Taudon in 1855. He divides the 

 genus Bythinia into two groups, (a). Bythinella — shells with 

 a cochleariform operculum, and an eccentric nucleus, (h). 

 Elona — operculum paralleliform, nucleus central. In reality 

 the genus is no more than Bythinia and Bythinella, the latter 

 including all the little French fiuviatile species with a spiral 

 operculum. Peringia is a genus recently erected h\ Paladilhe 

 for Turlo ulvce, a marine species." The latter does not con- 

 cern us, but I mention it lest its use should cause confusion. 



From all these considerations, therefore, it will be seen 

 that, in any case, the genus Paludestrina cannot be main- 

 tained under that name. It is not received by any modern 

 system writer except Chenu, and even he admits the priority 



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