134 College of Forestry 
tissue. The latter will be first considered. It will be remem- 
bered that Petersen observed that the bottom samples were 
made up of a top layer, brown and fluffy in appearance, which 
it was suggested formed a large part of the food of mollusks 
and other animals (see page 117). In Oneida Lake the sur- 
face of the bottom deposits, in bays and quiet bodies of 
water, is precisely this character, and no doubt is used by 
Spherium and Pisidium, both of which lie in_ this 
deposit. The Unionide, however, are probably not able to 
Fig. 36. Diagram illustrating quantity of mollusks in one square foot 
at station III, habitat 2, c, sandy bottom, water 2 feet deep, 
54 specimens present. 
. Campeloma integrum (2). 
. Amnicola lustrica (8). 
. Valvata bicarinata normalis 
(4). 
_ Planorbis campanulatus (1). 
. Planorbis hirsutus (1). 
b. Spherium vermontanum (10). 
z. Pisidium variabile (2). 
1. Pisidium compressum  (lavi- 
gatum (8). 
. Pisidium species (3). 
Pisidiwm species (4). 
. Gillia altilis (11). 
KQ O70 
bam 
4 
