The Productivity of f'ish Food in Oneida Lake 175 



gravel, and clay bottoms in water one and a half feet deep, but 

 the majority of individuals were young or immature. 



This form of trivolvis seems to be separable from the shell 

 typically known as trivolvis. It is ecologically different, living 

 in a more exposed habitat than does the typical form. If the 

 large, somewhat flat form, which is a species of swamps and 

 quiet waters, is Say's trivolvis then the wider-whorled form 

 herein indicated might bear the name of fallax Haldeman, 

 which evidently represents a shell of the kind figured (1. c, 

 fig. 46, Nos. 19, 20. See also trivolvis Nos. 13-16 of the same 

 figure. Compare these figures with Binney's, '65, p. 116, fig. 

 194, and p. 120, fig. 201). For ecological reasons it seems 

 necessary for this form to have a name. 



75. Planorbis binneyi Tryon. 



Common on a boulder shore in one-half to one and a half 

 feet of water. Collected on sand and clay bottoms in one and 

 a half to five feet of water. The majority of the individuals 

 were young or immature. Three young specimens were found 

 on a leaf of Sagittaria ari folia. 



76. Planorbis antrosus Conrad. 



This Planorbis occurs in many habitats, on all varieties of 

 bottom, in water from one and a half to 18 feet deep. It is 

 more abundant at a depth of one and a half to three feet on a 

 sand or clay bottom. It is usually associated with the fila- 

 mentous algae Cladophora and Qldogoninm and is also found 

 on floating leaves of Potamogeton natans. The majority of 

 individuals secured were young or immature and the adults 

 were smaller than is normal for the species. 



77. Planorbis campanulatus Say. 



Common on all varieties of bottom in water one to 9 feet 

 deep. It is more abundant on a sand bottom in water one and 

 a half to five and a half feet deep and also occurred on a mud 

 bottom in 9 feet of water. In most habitats it is associated 

 with filamentous algae, either Qidogonium, Spirogyra, or Clado- 

 phora fracta. About half of the individuals collected in 1916 

 were young or immature and the adults were below the normal 

 size, the greatest diameter observed being 1 1 and 14 mm. 



