FAMILY PHYSIDvE 



99 



Segmentina (Planorbula) christyi n. sp. Plate ii, figs. lo, ii. 



Slifll luscnililiiitT /'. armiifcra in a general way but having six 

 whorls, the upper surface nearly flat, the latter jxirt 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 strite, 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. arynigera . Max. diam. 10. o; 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 worthv of a 

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

 hundred from forty different localities, north and south, of P. art/ii- 

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

 sculptured of the group. 



Family PHYSIDiE. 

 Genus Physa Draparnaud. 



</yy'.f<zDRAPARNAUD, Tableau, pp. 31, 52, iSoi ; Hist, des Moll, de France, 

 pp. 25, 28, 54, 1805; first species Bulla fontiniilis Linne. — Roissv, 

 Moll., V, p. 343, 1805. — Studer, Syst. \'erz., p. 25, 1820. — Lamarck, 

 An. s. Vert., vi, pt. 2, p. 155, 1822. Not of Fitzinger, 1833, nor Wes- 

 terlund. 1902. 



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



Physa SowERBV, Genera, fasc. vii (Lifiincra ), 1822. — Fleiiixg, Brit. An. 

 p. 276, 1828. — Leach, Proofsheets, p. 150, Jidc' Turton, Man., p. 127, 

 1831. — Leach, Synops. Moll. Gt. Brit., p. 109, 1852. 



Rivkola Fitzinger, Verz. Conch., p. no, 1833. Type B. fpnthia/is Linne. 



<iPhysa BiN'NEV, Land and Fw. Sh. N. Am., 11, p. 75, 1865. — Dall, Ann. 

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



Physella HaldeiMAN, Mon. Limn., I, pp. 14, 38, 1842 ; type P. g!obosa 

 Hald. — Dall, op. cit., p. 355, 1870. 



Physodon Haldeman, Mon. Limn., I, pp. 14, 39, 1842; type P. viicrostoma 

 Hald. — Dall, op. cit., p. 356, 1870. 



? Diastropha Gray, in Turton, Man., ed. 11, p. 16, 1840; sole ex. Phvsa 

 contorta Michaud. — Haldeman, Mon. Limn., iii, 3d page of cover, 

 1841, text, pp. 14, 35, 1842. — MoQUiN Tandon, Hist. Moll. Fr., 11, p. 

 450, 1855. 



? Diastropha ' Guilding,' Gray (Synops. Brit. Mus., 1840, fide .^gassiz), 

 P. Z. S., 1847, p. 180; Physa giiildingii Sv/a.mson. 



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

 Drap. 



'yMacrophysa Meek (MS. 186;), Dall, Ann. Lye. X. H. N. Y., ix, p. 356, 

 1870 ; type Physa columnaris Desha\es, Eocene. 



