41 RESEARCHES L'PON THE HYDROBIIN.iE 



is synonymous with Ilydrohta. II. & A. Adams^ have rightly 

 understood Pfeiifer's genus, as their description shows, but most 

 of the species they refer to it, among' them our Littorinella 

 minuta, belong to groups entirely different. 



BYTHINELLA, Moq.-Tand. 



Leachia, Risso, Hist. Nat. d'Europe Meridionale, IV, (1826) 100, 102 (not 



of Lesueur, 1821). 

 Bytlilnella, Moq.-Tand., Jour, de Conch. II, (1851) p. 239, note ; and Hist. 



Nat. des Moll. ter. et fluv. de France, II, (1855) 515. 

 Suhulina, Trosch., Geb. der Schneck., I, (1857) 108 (not of Beck). 

 Paludinella, Frauenfeld, Verliandl. der k.-k. zool.-bot. Gesellschaft in 



Wien, XIII, (1803) 199 (not of Pfeiffer). 

 Microna, Ziegler, in Frauenfeld's "Arten der Gattung Lithoyhjphus Mhlf." 



etc., loc. cit. XIII, (1863).20O. 



Shell elongated-ovate, usually somewhat pupiform, imperforate, 

 or simply rimate ; apex obtuse. Aperture oval or rounded ; peri- 

 treme continuous, outer lip slightly thickened. Operculum corne- 

 ous, with the nucleus moderately large, dlnd not very close to the 

 basal margin. Tentacles tapering, but blunt at tip. Foot rather 

 narrow, rounded behind. Terge (in B. ferruaina) bifid. 



Lingual dentition of B. ihermalis, according to TroscheP : 

 Rhachidian tooth moderately long, with the infero-lateral angles 

 much produced. Intermediate tooth with the body longer than 

 broad. Formula of the denticles : t-^ - 6 - 18 - 0. 



Station, fresh water. 



Distribution, Europe and North America 



Type B. viridis, Moq.-Tand., Journ. de Conch., II, (1851) p. 239, note ; 

 and Hist. Nat. des Moll. ter. et fluv. de France, II, (1855) 524, pi. xxxix, 

 fig. 11-17. — Bulimus viridis, PoiR, Prodr., (1801) 45. — Cyclostoma viride, 

 Drap., Hist. Moll., (1805) p. 37. Bab. Western Europe. 



The following species may also be mentioned : — 



B.ferrusina, Moq.-Tand., Hist. Nat. des Moll. ter. et fluv. de France, II, 

 (1855) 516, pi. xxxviii, fig. 20-28. — Paludina ferrusina, Des Mont. 

 Western Europe. 



B. vitreu, Moq.-Tand., loc. cit., II, (1855) 518, pi. xxxviii, fig. 33-36.— 

 Cyclostoma vitreum, Drap. Western Europe. 



' Genera of Recent Mollusca, II, 315. 



2 Gebiss der Schuecken, I, 108, pi. viii, fig. 6. 



