238 Wisconsin Academy of Sciences, Arts and Letters. 
(See Walker, Nautilus, XIII, p. 133; Baker, Nautilus, 
NXII, p. 41). Binneyi is related to Palnorbis ammon 
Gould, but is apparently distinct. 
36. Planorbis trivolvis Say. 
Stations IV 2 , XIV 2 , XV. This species inhabits only 
quiet bodies of water which are more or less swampy. In 
such a habitat it is always abundant. The trivolvis of 
Tomahawk Lake are very large and the fully mature ex¬ 
amples suggest such names as me\gasoma DeKay and mac- 
rostomus Whiteaves which are probably to be considered 
but different phases of development. 
Family Lymnaeidae. 
Genus Lymnaea Lamarck. 
37. Lymncea stagnalis appressa Say. 
Station XIII 1 . Stagnalis appressa lives only in the more 
open part of a swamp-bordered thoroughfare. The shells 
are here quite uniform and closely resemble the typical 
form. At Station XIII 1 the habitat was a protected, lake¬ 
like bay at the head of a wide thoroughfare and the shells 
were found on floating logs or on the sandy bottom in shal¬ 
low water. 
38. Lymnoea stagnalis lillianoe Baker. 
Station IV 1 , VII, IX, X, XIV 3 . All of these stations 
were on more or less exposed shores, subject to the force of 
the waves. Lillianoe is typically an inhabitant of sandy 
shores, in shallow water, where it is subject to heavy wave 
action. When any number of specimens were found, the 
habitat was invariably an exposed beach. Individuals 
were observed crawling over the sandy beach or attached 
to water soaked logs or other shore debris. The animal of 
this race exhibits two color modifications, one bright yel¬ 
low and the other black or grayish-black. No cause for 
this color dimorphism was apparent. It is not protective, 
as both forms occupy the same area of white sandy beach. 
