FAMILY LYMNyEID.-E 97 



Range. — Europe, Algeria, in the Old World ; in America at Cari- 

 bou, Aroostook Co., Maine ! Hamilton and Ottawa, Canada ; Ann 

 Arbor, Michigan ! Red Deer in Alberta ; Manitoba. 



This small and inconspicuous species will doubtless be found in 

 many other localities when thorough search is made. 



Genus Segmentina Fleming. 



Segmentina Fleming (1817, Edin. Encycl., ed. vii, vol. xii, fide Turton 

 Manual, p. 116, 1831); Brit. An., p. 279, 1S28. Type Nau/i/us lacus/n's 

 (Lightfoot) Montagu. — Halde.man, Mon. Limn., iv, p. 14, 1842. — 

 Stein, Schnecken u. Musch. Berlins, p. 78, 1850. — Westerlund, 

 Fauna Pal. Reg., v, p. 85, 1885. — \\'oouward, List. Bnt. Nonmarine 

 Moll., p. 355, 1903. 



Hemithalamus Leach (1819), Proofsheets, p. 137, 7?^/^ Turton, Manual, |). 

 116, 1831. — Fitzingek, Syst. Verz., p. no, 1833. — Rossm.Kssler, 

 Icon., I, pt. II, p. 15, 1835. — //. nilidus (Muller) Leach = /". lincatus 

 Jeffreys. 



&^Wd;;/a«iZ SwAiNSON, Malac, p. 337, 1840 ; lapsus pro Seginentina Fleming. 



Hippeiitis (sp.) AOASSIZ in Charpentier, Fauna Helvetica, p. 22, 1837. — 

 Hartmann, Syst. Uebers, tab., 1840. 



Dentatus Gray, P. Z. S., 1847, p. 181, not of Beck, 1837, P. armatiis Gray ; 

 ? = /*. annigerus Say + P. armigcr Beck. 



> Ptanorbula Haldeman, Mon. Limn., iv, p. 14, 1842, P. armigcnis Say. 



Discus Haldeman, Mon. Limn., i, p. 4 of cover, July, 1840 {P. armigerus 

 Say), not of Fitzinger, 1883. 



This genus was founded by Fleming on the Planorbis nitidus of 

 Muller, of which lacustris Lightfoot, is a synonym. I have not been 

 able to verify the reference to the Edinburgh Encyclopedia. Leach's 

 name was circulated in proof sheets, but not actually published or cited 

 by other authors until after Fleming's description appeared. Beck called 

 a group of Planorbes '•Dentait' but applied no name to the group, 

 and the transformation by Gray to ' Dentatus^ as if it had been in- 

 tended for a generic or subgeneric name, seems quite unwarranted. 



The genus may be divided into three groups as follows : 

 Subgenus Segmentina s. s. Base flattened, coil close, margin of the 

 aperture simple, sharp ; lamellae ridgelike, several sets persistent in 

 the adult. Type P. nitidtts Muller. Palearctic region. 

 Subgenus Planorbula Haldeman. Whorls rounded, coil loose, mar- 

 gin of the aperture simple, sharp, slightly expanded ; lamella denti- 

 form, only one set persistent in the adult. Type, P. armigerits 

 Say. Nearctic region. 

 Haldcmanina Dall, n. sect., whorls carinate above and below, margin 

 of aperture thickened and reflected ; lamella complex, dentiform 

 and ridgclike, one series persistent in the adult. Type, Planorbis 

 ■whcatlcyi I>ea. Coosa drainage of Alabama. 



