142 C. A. Westerlund, Synopsis Molluscorum Extramarinor. Scanclin. 



Fam. Neritinida?. 



Testa scepius crassa, semiglobosa [supra convexa, suh- 

 tus plana), transversalis, columella plana, latissima, clecU- 

 vis, margine acuta, spira hremssima, excentrica, opercu- 

 lum (bispirale), articulatum calcareum, firmum. 



Gen. Neritina Lam. 



N. fluviatilis Lin. (Syst. Nat. X, 1758, Nerita). T. oblonga, pal- 

 lide virescens (violascens v flavescens), striatula, lineis et 

 maculis fuscis reticulata, siepe fasciis tribes fuscis obso- 

 letis ornata, spira brevi, depressa; apert. semicircularis, 

 intiis pallide virescens, plaga columellari pallida; opercu- 

 lum crocaceum, margine miniato. Long, transv. 10 — 12, 

 alt. apert. 7 — 8 mm. 



Hah. Siiecia, in provinciis litoralibus orientalibus saltern 

 usque ad ostium fluvii Dalelfven, formse fluviatiles et lacustres 

 prsecipue in prov. Skane, ceteroquin forma baltica ubique prse- 

 valens vel sola, sed nulla forma in provinciis internis inventa. 



— Now. passim ad ostia fluviorum et rivorum (fide H. Friele). 



— Dania in una alterave forma vulgaris, typica rara excepta. 



— Fennia tantummodo forma baltica. 



Var. fontinalis Brard (Coq. de Paris, 1815) : t. tenuis, pellucens, 

 fusca, albomaculata. — Forma rivalis. 



Var. lacustris Lin. (Fauna Suec. ed. 2, 1761, Nerita): t. tenui- 

 uscula, coerulescens v. pallide virescens, variis modis picta, 

 intus cum plaga columellari crocea v. citrina, spira elata; 

 long, transv. 9—12 mm. — Suecia in Skane multis locis. 

 — Dania in lacubus et in rivis ad lacus. 



Var. spirata VV. (Fauna Suec, 1873): t. crassissima, calcarea, 

 albida, unicolor v. lineis fuscis reticulata, antice interdum 

 rufostrigata et costulis transversalibus irregularibus, intus 

 crocea, operculo et plaga colum. subviolaceis v. flavescenti- 

 bus, opercul., margine ssepe atro, spira alta, elata, anfr. 

 penult, convexus, apertura marginibus saepe callo crasso 

 junctis; long, transv. 11, alt. 9 mm. (spec. max). — Suecia 

 in Gotland (in palude ad Fardume * et ad Ar frequens). 



Forma minor, long. tr. 7, alt. 5 mm. — Suecia in Gotland cum 

 typo, Up)land ad Ultuna. 



