Animals of the Mississippi Bottoms near Quincy. 153 



Prof. Forbes has shown in his papers on the food of fishes, they 

 constitute a large item of the food of some of our best fishes. 

 The great abundance in which they occur in the water of this 

 region must give them a decided influence, as competitors for 

 food. 



Of the two families appearing in the Quincy collection, 

 the first is represented by small species which commonly pass 

 for the young of the true clams (Unionidas) of the second 

 family. That they are adult animals is, however, easily shown 

 with a magnifying glass, since by its means they may be seen 

 in many cases to contain living young of relatively large size. 

 The shells of these bivalves are not commonly more than half 

 an inch in length. 



Family Corbiculid^. 



Sphcerium solidulitni, Prime. 



{Cyclas solidula^ Prime, Proc. Bost. Soc. Nat. Hist., iv, 158, 

 1851.) ' 



Common in shallow water in Willow Slough. 



Sphcerium transversiim^ Say. 



(Cyclas transversa, Say, New Harmony Disseminator, ii, 

 346,1829.) 



Frecpent in several of the pools. 



Localities: Willow Slough, Long Lake, Broad Lake, Wood 

 Slough. 



Family UifiGNiD^. (River Clams.) 



Anodonta grandis, Say. 



(Say, New Harmony Disseminator, i, 341, 1840.) 

 This large, smooth, thin-shelled clam is common in most 

 of the sloughs and lakes. It is probably the species which the 

 channel catfisli manages to tear from its shell. The shells re- 

 cently emptied were sometimes brought out by seines in great 

 numbers. Young and adults were seen in the sloughs and 

 lakes, one of the former measuring .62 inch in length. A valve 

 of a large one, picked up at the edge of Wood Slough, measured 

 6.75 inches in length. 



Localities: Lily Lake, Broad Lake, Wood Slough. 



