THE NAUTILUS. 



91 



a name. It is suggested that the name /ailax of Haldeman is 

 applicable and seems to represent a shell of the kind here 

 indicated. 



Planorbis binneyi Tryon. Common on a boulder shore in one 

 half to one and a half feet of water. Also collected on sand 

 and clay bottoms in one and a half to five feet of water. The 

 majority of the specimens were young or immature. Three 

 young individuals were found on a leaf of Sagittaria arifolia. 



Planorbis antrosus Conrad. Occurs on all varieties of bottom, 

 in water 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, and is usually associated with the filamentous algae 

 Cladophora and Oedogonium. Also found on floating leaves of 

 Potamogeton natans. The majority of individuals were young or 

 immature and the adults were smaller than normal. 



Planorbis campanidatus Say. Common on all varieties of 

 bottom in water 1-9 feet. deep. It is most abundant on a sand 

 bottom in 1^-5 feet of water. In most habitats it is associated 

 with filamentous algae (Oedogonium, Cladophora, Spirogyra). 

 About half the individuals collected were young or immature. 



Planorbis parvus Say. Occurs on all varieties of bottom in 

 water 1^—12 feet deep, but is most abundant on clay, sand, and 

 mud bottoms in water 1^—4 feet deep. It is usually rarest on 

 boulder bottoms, but on a shoal north of Dunham Island a 

 single boulder 6x4x3 inches had 15 parvus on its surface. This 

 species is usually associated with the algae mentioned under the 

 last species and is also frequently found on the leaves of Nym- 

 phaea, Castalia, Sagittaria arifolia, Myrioyhyllum, and Potamogeton 

 interruptus and Richardsoni. Parvus is the most abundant Plan- 

 orbis in the region the algae in many places being filled with 

 this species and one of the Amnicolas. 



Planorbis hirsutus Gould. This species occurs on all varieties 

 of bottom except clay, in water 1J-9 feet deep, being most 

 abundant at 3-4 feet on a sand bottom. Rare on boulder and 

 gravel bottoms. Associated with filamentous algae. 



Planorbis deflectus Say. This species is apparently rare in 

 Lower South Bay occurring in but three habitats, on a gravel 

 bottom in 2J feet of water. 



