Baker—Molluscan Fauna of Tomahawk Lake, Wisconsin. 239 
Specimens living in protected bays have a longer spire 
and more closely resembles appressa, clearly showing that 
lilliance is a modification of this race. 
Genus Pseudosuccinea Baker. 
39. Pseudosuccinea columella (Say). 
Stations II 2 , XI, XIII 2 , XIV 1 . Columella always oc¬ 
cupies a still water or swampy habitat, its situs being 
usually the under side of lily leaves or on floating debris. 
Genus Bulimnea Haldeman. 
40. Bulimnea megasoma (Say). 
Stations XIII, 1 XXIII. This large, fine Lymnsea lives 
in swamps where the water is quiet. The bottom of such 
a habitat is boggy and the water is so shallow that frequent¬ 
ly little boggy islands are formed, and on these megasoma 
may be found, one or two specimens on each island. In 
other parts of this habitat they may be found near the 
shore, clinging to logs and other debris. A small swampy 
slough, lying between the Wisconsin Biver and Gilmore 
Creek, afford the best habitat for megasoma, where it lived 
in considerable number. This slough is about a quarter 
of a mile long and two or three hundred feet wide. The 
water is (in summer) but a few inches in depth, but the 
mud which is about the consistency of mush, is six 
or more feet in depth. Megasoma lives on the surface of 
the mud and on old logs which the lumbermen have left 
in the swamp. It would seem that the characteristic 
habitat of this species is a swamp or marshy pond or bay. 
The individuals of this species are very large and fine, 
a length of 47 mill, being frequently attained. The epi¬ 
dermis is olive green or greenish chestnut, and the surface 
of the last whorl is either heavily malleated or shows more 
or less equidistant riblets parallel with the growth lines. 
The spire varies from elevated to depressed. 
