92 THE NAUTILUS. 



Planorbis exacuons Say. Occurs on all varieties of bottom in 

 1^15 feet of water. Most abundant on sand and mud bottoms 

 in 2-5 feet of water. It is rare on gravel bottom but is fairly 

 common on boulder bottom, two to four individuaLs being 

 found on each stone. 



Segvientina (irmigcra (Say). This species was collected in 

 two habitats, one a swampy shore in Short Bay among the alga 

 Oedoganium and the other in a protected bay on the north side 

 of Frenchman Island, on leaves of Sagittaria arifulia. Both 

 habitats are in shallow water with mud bottoms. 



Lymnaeidae. 



Lymnaea stagnalis lillianae Baker. This, the largest of the 

 gastropods in the lake, was found only in one habitat, the 

 rocky shore of the lake, east of Norcross Point, in water a few 

 inches to two feet in depth. All were immature, half or three- 

 quarters grown. A single young shell (dead) 14 mm. in length 

 was found in a small bay on the south shore of Long Point in 

 water 3^ feet deep, but it had evidently been brought there from 

 some other habitat. 



Pseudosuccinea columella chalybea (Gould). Collected in two 

 habitats, a protected bay on Nymphcea leaves, and a partly en- 

 closed lagoon among filamentous algse, Oedogonium. All speci- 

 mens were immature. 



Acella /iaide?)ia7ii ( " Deshayes " Binney). Observed in two 

 habitats on submerged vegf-tation, always in a protected situa- 

 tion, in water from 1 — 4 feet deep. All of the specimens were 

 young, none exceeding 10 mm. in length, and were invariably 

 found on the narrow leaves of Potamogeton interruptus. For the 

 ecology of this species see the Nautilus, XXX, pages 135-138. 



Galba catascopium (Say). One of the most abundant of 

 Oneida Lake mollusks, found on all varieties of bottom in water 

 1^ to 14 feet deep. It is most abundant on sand and mud 

 bottoms, associated with filamentous alga, when young, and 

 on boulder and gravel bottoms when adult. 



Galba obrussa (Say). A single dead shell of this species was 

 found in a dredging on a bar near a small lagoon east of the 

 steamboat landing in 1^ feet of water. It was young, 5 mm. 



