FAMILY PHYSID^E 99 



Segmentina (Planorbula) christyi n. sp. Plate n, figs. 10, n. 



Shell resembling P. armigera in a general way but having six 

 whorls, the upper surface nearly flat, the latter part of the last whorl 

 in nearly the same plane as the preceding whorls, with no marked 

 deflection ; the whorls rounded, with no carina above or below ; the 

 surface sculptured with fine close silky incremental lines and fine sharp 

 spiral striae, giving a minutely reticulate effect when magnified ; aper- 

 ture-plane about 25 from the vertical ; teeth very similar in form and 

 position to those of P. armigera. Max. diam. 10.0; min. diam. 7.5 ; 

 height 3.0 mm. 



High Bluff, Manitoba ! (R. Miller Christy) ; Fort Smith, Mackenzie 

 River! (E. A. Preble). 



After comparing these shells with a large series of P. armigera and 

 finding nothing intermediate, I conclude that this form is worthy of a 

 name. I have examined seven specimens of P. christyi, and several 

 hundred from forty different localities, north and south, of P. armi- 

 gera. The present form is the largest, flattest, and most sharply 

 sculptured of the group. 



Family PHYSIDJE. 

 Genus Physa Draparnaud. 



<^Physa DRAPARXAUD, Tableau, pp. 31, 52, 1801 ; Hist, des Moll, de France, 

 pp. 25, 28, 54, 1805; first species Bulla fontinalis Linne. ROISSY, 

 Moll., v, p. 343, 1805. STVDER, Syst. Verz., p. 25, 1820. LAMARCK, 

 An. s. Vert., vi, pt. 2, p. 155, 1822. Not of Fitzinger, 1833, norWes- 

 terlund, 1902. 



Enydra HUBXER, Zwei Briefe, 1810 (nomenclature non-Linnean ?). 



Physa SOWERBY, Genera, fasc. vn (Lzmn&a), 1822. FLEMING, Brit. An. 

 p. 276, 1828. LEACH, Proofsheets, p. 150, fide Turton, Man., p. 127, 

 1831. LEACH, Synops. Moll. Gt. Brit., p. 109, 1852. 



Rivicola FITZIXGER, Verz. Conch., p. no, 1833. Type B. fontinalis Linne. 



<_Physa BINNEY, Land and Fw. Sh. N. Am., n, p. 75, 1865. DALL, Ann. 

 Lye. X. H. N. Y., ix, p. 355, 1870. Type P. fontinalis. 



Physella HALDEMAX, Mon. Limn., i, pp. 14, 38, 1842 ; type P. globosa 

 Hald. DALL, op. cit., p. 355, 1870. 



Physodon HALDEMAX, Mon. Limn., i, pp. 14, 39, 1842; type P. microstoma 

 Hald. DALL, op. cit., p. 356, 1870. 



? Diastropha GRAY, in Turton, Man., ed. n, p. 16, 1840; sole ex. Physa 

 contorta Michaud. HALDEMAN, Mon. Limn., in, 30! page of cover, 

 1841, text, pp. 14, 35, 1842. MOQUIX TAXDOX, Hist. Moll. Fr., n, p! 

 450, 1855. 



? Diastropha 'Guilding,' GRAY (Synops. Brit. Mus., 1840, fide Agassiz), 

 P. Z. S., 1847, p. 1 80 ; Physa guildingii Swainson. 



<Phyza Risso, Hist. Nat. Eur. Men, rv, p. 96, 1826; .st sp. P. fontinalis 

 Drap. 



~>Macrophysa MEEK (MS. 1865), DALL, Ann. Lye. N. H. N. Y., ix, p. 356, 

 1870; type Physa columnaris Deshayes, Eocene. 



