176 College of Forestry 



78. Planorbis parvus Say. 



This little wheel-snail occurred on all varieties of bottom in 

 water one and a half to 12 feet deep, but was most abundant 

 on sand, clay, and mud bottoms in water one and a half to 

 four feet deep. It was found plentifully in one dredging in 9 

 feet of water on a mud bottom. It is rarest on boulder bot- 

 toms, but on a boulder shoal north of Dunham Island a stone 

 6x4x3 inches was covered with 15 parvus, adult and young. 

 Parvus is usually associated with filamentous algse (CEdogo- 

 nium, Spirogyra, or Cladophora) and is frequently common on 

 lily leaves (Nyinplicea and Castalia), Myriophyllwn, and the 

 pond-weeds Potamogeton interriiptus and richardsonii. A 

 few specimens have been found on the arrow-head, Sagittaria 

 arifolia. It is the most abundant of the whell-snails, the algse 

 in many places being filled with it and Amnkola. The major- 

 ity of individuals obtained were adult, though smaller than is 

 normal for the species. 



79. Planorbis hirsutus Gould. 



The Hairy Whell-snail occurred on all varieties of bottom, 

 except clay, in water one and a half to 9 feet deep, but was 

 most abundant at 3 to 4 feet on a sand bottom. It was rare 

 on boulder and gravel bottoms. Associated with filamentous 

 algse, Qldogonium, Spirogyra, and Cladophora, rarest in the 

 latter. The majority of individuals were young or immature. 



*8o. Planorbis defiectus Say. 



Examples of this small Planorbis were found in three habi- 

 tats. In but one of which it was collected alive, on a gravel 

 bottom in two and a half feet of water. Several dead shells 

 were collected, one of which, 5 mm. in diameter, had a well- 

 marked median carina on the body whorl and the aperture 

 was notably deflected. This species is apparently not common 

 in Oneida Lake. 



81. Planorbis exacuous Say. 



Occurs on all varieties of bottom in one and a half to 15 

 feet of water. Most abundant on sand and mud bottoms in 

 two to five feet of water. It is rare on a gravel bottom but is 



