12 MUSSEL FAUNA OF THE KANKAKEE BASIN. 



considerable water into the lake. There is an old outlet at the south- 

 east corner of the lake, which formerly drained into the Yellow 

 River. Although the mouth is closed by a sand bar, the water in 

 the lake occasionally rises high enough to overflow this and run into 

 the river. The bottom of the lake is firm sand and gravel, and the 

 shores slope olf rapidly into deep water, the depth being 40 feet 

 at the center. 



It is a very clean lake and in this respect presents a marked con- 

 trast to the Lake of the Woods. For vegetation pickerel weed 

 {Pontederia) was common around the shores, the largest patch being 

 along the northern margin. The broad-leaved pondweed {Potaiaoge- 

 ton amylifolius) and Robbins's pondweed {P. rohhhisli) were found 

 in large patches, and Chara, probably fcBtida^ was also common. 

 There were j^lenty of w^hite water lilies but no spatterdock {Nym~ 

 'phoea). Great patches of ditch moss {Pkilotria) , considerable wild 

 celery {V allisneria) and horn wort {C eratophyllum) ^ and some 

 Naias, Cladophora, bladder wort ( Utricularia) , and Decodon, and in 

 one place some Nostoc were found in shallow water. The Avater tem- 

 perature at the surface near the center of the lake Avas 79° F. ; the 

 plankton was very light, containing no vegetation and but a few 

 water fleas {Gladocera). 



A careful examination of the entire margin of the lake yielded 

 eight specimens of L. luteolus, widely scattered, and a half dozen A. 

 grandis. The mussels were too far apart to breed w^ell and all were 

 stunted in size and peculiarly fragile at the hinge. 



For food the stomachs of the A. grandis contained one Cosmarium, 

 two or three Ccelosphcei'iunis, a few Clathrocystis, and one Ascaris. 

 In the L. luteolus were found one Anurwa and a little Clathrocystis 

 mixed in a dark gritty mass. Here where the mussels are nearly 

 starved they seem to digest w^ell. (It is common where food is 

 abundant to find undigested organisms at the posterior end of the 

 mussel's intestine, but such was not the case here.) 



Station 7. Yellow River at IIih7)ard. — The water of the river 

 here was perfectly clear and had a maximum depth of 3 feet. The 

 bottom was of fine sand, coarse gravel, and here and there a mud 

 bar, particularly along the shore. The current was rather slow, not 

 more than 2| miles an hour, and the temperature was 78° F. 



For vegetation there were lodged masses of algae, some Cladophora, 

 and patches of the river pondweed {Potamogeton fluitmis) and 

 aquatic moss. There were also many small sponges scattered over 

 the rocky parts of the bottom. A large number of young black bass, 

 some Johnny darters {Boleosoma nigrum)^ and a few black-sided 

 darters {Hadroptems aspro) were found on the mussel beds. Only 

 a few mussels were found in the muddy places, chiefly U. gibhosus, 



