136 College of Forestry 
before being eaten, as Physa is not known to eat living ani- 
mal food. As has been already stated, Physa lives on both 
vegetable and animal f« sod, but does not attack living animals ; 
Planorbis lives entirely on plants; while Lymivea eats plants 
and animals, dead or living, and even commits cannibalism. 
Ancylus is known to eat only plants, mostly decaying 
material. Campeloma is scavengiferous as well as phyto- 
phagous, Dr. C. C. Adams having observed species of this 
genus feeding on a dead fish on the shore of a small stream 
tributary to the Desplaines River, near Riverside, Hlinois. 
Fig. 37. Diagram illustrating quantity of mollusks in one square foot 
at station 1, habitat 2, ¢, vegetation, Castalia odorata, 
10 specimens present. 
1. Acella haldemani (3). 3. Physa ancillaria warreniand 
2. Pseudosuceinea columella chaly- (2)5 
bea (5). 
