236 Wisconsin Academy of Sciences, Arts and Letters. 
Submenus Helisoma Swainson. 
31. Planorbis campanulatus Say. 
Stations III, IV 1 , VI, VII, IX, X, XIII 2 , XIV s . 
This Planorbis apparently prefers a habitat where wave 
action is marked. It is the commonest Planorbis in this 
region, living on the sandy, or pebbly shore in a few inches 
of water. 
32. Planorbis campanulatus rudentis Dali. 
Stations II 1 III, IV 1 , VI, VII, IX, X, XII. 
A large number of the campanulatus in Tomahawk Lake 
appear to be referable to Balks rudentis (Alaska Moll. p. 
90) characterized by a large shell and particularly by the 
elevation of the apical whorls above the body whorl, much 
as in Planorbis multivolvis Case. The apical whorls are 
flat as in typical campanulatus, the deflected body whorl 
beginning at about one-third of the last whorl. In typical 
campanulatus the whorls are usually coiled in the same 
plane, the apical whorls being a little below the dorsal mar¬ 
gin of the body whorl. The specimens mentioned by Wal¬ 
ker, from Siskowit Lake, Isle Royale, are probably also 
this variety (An. Rep. Mich. Geol. Surv. p. 293). The 
Tomahawk Lake campanulatus are more variable than 
specimens from Xew York and Illinois. 
33. Planorbis bicarinatus striatus Baker. 
Stations II 1 III, VII, VIII, XII. Very common on 
logs and on sand and pebbles in a few' inches of water. 
Prefers open shores. 
All of the bicarinatus living in Tomahawk Lake seem 
referable to this race. The spiral striation is very conspic¬ 
uous and is well marked on the majority of the specimens 
secured. In typical bicarinatus from Xew York state 
(near Owasco Lake) the spiral sculpture is faint or lack¬ 
ing. 
34. Planorbis bicarinatus unicarinatus Haldeman. 
Stations XIV 2 , XV. This distinct race was seen only 
in a swampy bay and the quiet waters of a small creek, 
