124 THE CHICAGO ACADEMY OF SCIENCES. 
Section Polyrhytis Meek. 
Section Acella Haldeman. 
Section Pleurolimnea Meek. 
Section Galba Schrank. 
Subgenus Stagnicola Leach. 
Section Stagnicola S. S. 
Section Leptolimnea Swanison 
Section Physastra Tapp-Can. 
Genus Erinna Adams. 
In 19031 Dybowski proposed a etassification of the fresh-water 
pulmonates in which six families were recognized, as follows: 
Limneide 
Limnophyside 
Amphipeplidz 
Planorbide 
Ancylide 
Physidee 
This author thus tabulates the characters of the several groups: 
I. Mantel mit einem tiber das Gehause aufgeschlagmen Anhange. 
1. Zahnplatten mit einem flugelartigen Anhange, alle gleichformig 
gestaltet. Family PHysip&. 
2. Zahnplatten ohne Anhang, der Gestalt nach drei Gruppen beldend. 
Family AMPHIPEPLID2®. 
II. Mantel normal, ohne Anhange. 
1. Gehause in die Lange gestrickt. 
(a) Letzter Umgang sehr gross, bauchig aufgetrieben; Schale 
unregemassig quergestreift; Glasur weisslich; Lippe fehlt. 
Family LIMN#&ID. 
(b) Letzter Umgang ausgezogen, wenig gewolbt; Schale sehr 
fein und ziertich langs und quergestreift; Glasur 
rotlich; Lippe rotbraun. Family LIMNOPHYSID. 
2. Gehause in die Quere gestrickt. 
(a) Gehause scheibenformig. Family PLANORBID2. 
(b) Gehause mutzenformig. Family ANCYLIDA. 
In the above classification only the shell, mantle and radula are 
used as diagnostic factors. It is probable, however, that a study of 
the genitalia, nervous system and pallial organs will bear out the 
grouping substantially as proposed by Dybowski. The separation of 
Limnophysa from Lymneidz as a family is, however, not borne out 
by present studies, there being no distinguishing features by which 
the group can be separated from the other Limnzide, except as a 
genus. 
In the present monograph it is proposed to classify the Lym- 
nzids by the characters of the shell, genitalia (shape of prostate, rela- 
tive size and form of penis and penis-sac) and radula. The study of 
1Nach. Deutsch. Mal. Ges., XXXV, pp. 130-144. 
