HANXIBAL : CALIFOKXIAN FRESHWATER MOLLUSCA. 185 



district. The shell characters oUer only partial satisfaction in their 

 discrimination. , , ,, .. 



Genus Amnicola, Goukl & Haldenian. ""^ 



r<ihi(//na (sp.), Say, 1819 (P. limosa, Say) ; Amnicola, Gould and 

 Haldenian, in Haldenian, 1840, no species cited; in Gould, 1841 

 {P. porata, Say {= P- limosa, Sav), first species, cited by 

 H. & A. Adams, 1854). 

 Type, Paludina limosa, Saj'. 



Shell of moderate size, averaging 4 mm. in altitude, conic-globose, 

 sub-perforate, epidermis pale horn-coloured, whorls inflated, sutures 

 impressed, spire regularly elevated, apex small and obtuse, aperture 

 ovate, peritreme continuous ; habitat quiet streams, lakes, and springs. 



Amnicola limosa (Say). 

 Paludina limosa, Say, 1817; P. porata, Say, 1821; A. parva, 

 Lea, 1841. 

 Shell large for genus, globose-conic, sutures impressed, spire 

 elevated ; habitat quiet streams and lakes. 



Boreal portions of American Province. Utah System. 



Quaternary : Loess of eastern States ; Bonneville Lake beds, Utah. 



Amnicola micrococcds, Pilsbry. 

 Amnicola micrococcus, Pilsbry, in Stearns, 1902. 



Shell minute, globose-conic, spire somewhat elevated, sutures barely 

 impressed; habitat springs. 

 Mojave System. 



Unrecognized: Amnicola ahavia, Mayer, 1869. Miocene (?) of 

 Alaska. 



Genus Paludestrina, d'Orbigny. 

 Bidimiis (sp.), Poiret, 1801 {B. viridis, Poir.) ; Turbo (sp.). Vail, 

 1801 {T. griseus. Vail = P. viridis, Poir.); Cyclostoma (sp.), 

 Draparnaud, 1801 (C vitreum, Drap.); Hydrohia (sp.), Hart- 

 mann, 1821 (C vitreum, Drap.); Paludina (sp.), Hartmann, 

 1821 {B. viridis, Poir.) ; Leachia, Eisso, 1826 ( C. vitrea, Drap.), 

 not Leachia, Lesueur, 1821; Paludestrina, d'Orbigny, 1840 

 {Paludina acuta, Desh.) ; Amnicola (sp.), Haldenian, 1844 

 {A. attenuala, Hald. = Paludina JVickliniafia, Lea) ; Bithinia 

 (sp.), Dupuy, 1849 {B. viridis, Poir.) ; Bythinella, Moquin- 

 Tandon, 1851 {B. viridis, Poir.); Melania (sp.), Conrad, 1855 

 (if. exigna, Conr. = A. protea, Gld.) ; Heleohia, Stimpson, 1865 

 {Paludestrina cuhninea, d'Orb.), preocc. ; Tryonia, Stimpson, 1865 

 {T. clathrata, ^t\m^. = A. protea, Gld.); Stimpsonia, Clessin, 

 1878 {Paludina Nickliniatia, Lea). 

 Type, Paludina acuta, Deshayes. 



Shell small or minute, averaging 4 mm. in altitude, elongate-conic 

 or attenuate, sub-perforate, whorls inflated, epidermis pale horn- 

 coloured, spire regularly elevated, apex small and obtuse, aperture 

 ovate, peritreme incomplete ; habitat lakes, streams, and springs. 

 The writer entertains doubts that the American species are true 



