FAMILY LYMN^EID^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 Segmenting Fleming. 



Sfgmentina FLEMING (1817, Edin. Encycl., ed. vn. vol. xn, fide Turton 

 Manual, p. 116, 1831); Brit. An., p. 279, 1828. Type Nautilus lacustris 

 (Lightfoot) Montagu. HALDEMAN, Mon. Limn., iv, p. 14, 1842. 

 STEIN, Schnecken u. Musch. Berlins, p. 78, 1850. WESTERLUND, 

 Fauna Pal. Reg., v, p. 85, 1885. WOODWARD, List. Bnt. Nonmarine 

 Moll., p. 355, 1903. 



Hemithalamus LEACH (1819), Proofsheets, p. 137, fide Turton, Manual, p. 

 116, 1831. FITZINGER, Syst. Verz., p. no, 1833. ROSSMASSLER, 

 Icon., I, pt. ii, p. 15, 1835. H. nitidus (MULLER) LEACH = P. lineatus 

 Jeffreys. 



Segmentaria SWAINSON, Malac., p. 337, 1840 ; lapsus pro Segmentina Fleming. 



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

 HARTMANN, Syst. Uebers, tab., 1840. 



Dentatus GRAY, P. Z. S., 1847, P- *8i, not of Beck, 1837, P. armatus Gray ; 

 ? = P. armigerus Say -f- P. armiger Beck. 



> Planorbula HALDEMAN, Mon. Limn., iv, p. 14, 1842, P. armigerus 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 ^ Dentati ' 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 ; lamellas ridgelike, several sets persistent in 

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

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

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

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

 Say. Nearctic region. 



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

 of aperture thickened and reflected; lamella? complex, dentiform 

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

 tvkeatleyi Lea. Coosa drainage of Alabama. 



