The Relation of Mollusks to Fish in Oneida Lake 261 
Genus Pisipium Pfieffer. 
20. Pisidium ferrugineum Prime. Not figured. 
A single specimen of this species was collected at station 
XXXI, habitat I, C. This is an eastern species listed by 
both Letson and Beauchamp. 
21. Prsidium variable Prime. Fig. 45, No. 25. 
Collected at three stations, on a sandy bottom in partly 
protected bays. A widely distributed species, listed from 
Lake Michigan, Saginaw Bay and Isle Royale. Listed by 
Beauchamp. 
22. Pisidium compressum Prime. Fig. 45, No. 27. 
Collected at station ILI, habitat 2, on a sandy bottom in a 
protected bay. Widely distributed, and reported from Lake 
Michigan, Traverse Bay and Saginaw Bay. Listed by 
Beauchamp. 
25. Pisidium compressum levigatum Sterki. Fig. 45 
No. 26. 
? 
Collected at four stations. Common at three, abundant at 
one. Widely distributed. Described after Beauchamp’s list 
was published. 
24. Pisidium equilaterale (Prime). Fig. 45, No. 28. 
Collected from two stations, one a sandy exposed bay, the 
other a protected bay with vegetation. It was very rare at 
both localities. Listed from New York by Letson but not 
by Beauchamp. 
25. Pisidium henslowanum (Sheppard). Not figured. 
This species was collected at the same stations as the last 
species, common at one and rare at the other. Dr. V. Sterki 
refers this Pisidium to this species with some doubt. They 
‘are peculiar in having a ridge or crest on the beak. The 
same form has been observed by Sterki from Ontario. 
Eaten by the Common Sucker. 
