94 Bryant Walker 



Lymn.^a coorERi Hannibal. 



LymncEa Cooperi Hannibal, Proc. Mai. Soc. Lond., X, 1912, p. 143, pi. VI, 



fig- 13a — c. 

 Type locality : Spring at AVright's, Santa Cruz Mountains, Cal. 



Lymn^a montanensis Baker. 



Lymncea montanensis Baker, Naut., XXVI, 1913, p. 115. 

 Type locality : Hayes' Creek, Ward, Montana. 



Family PLANORBID^. 



Subfamily PLANORBIN^ H. and A; Adams, 1858. 



Genus PLANORBIS Miiller, 1774. 

 Dr. Dall (32, p. 80) has proposed the following arrangement of this 

 genus : 



Subgenus Planorbis s. s. 

 Type Planorbis corneus Miiller. 



Section Plaiiorbina Haldeman. 

 Type P. olivaceus Spix. 



Subgenus Helisoma Swainson. 

 Type P. bicarinatiis (Say) Sowerby. 



Section Pierosoma Dall. 

 Type P. trivolvis Say. ■ 



Section Planorbella Haldeman. 

 Type P. cmnpanulatns Say. 



^ Subgenus Tropidiscus Stein. 

 Type P. umbilicatus Miiller. ■ 



Subgenus Hippeutis Agassiz. 

 Type P. fontanus Lightfoot. 



Section Menetiis H. and A. Adams. 

 Type P. opercnlaris Gould. 



Subgenus Gyranlns Agassiz. 

 Type P. alb us Miiller. 



Section Torquis Dall. 

 Type P. parznis Say. 



Section Armiger Hartmann. 

 Type P. crista h- 



For a criticism of Dall's arrangement, see Kennard (64, p. 47) and 

 reply by Dall (33, p. 141). 



Brown and Pilsbry have proposed (15, p. 212) a new section, Trop- 

 icorbis, type P. Uebmanni Dkr., but without any definition. 



