4 



MUSSEL FAUNA OF THE KANKAKEE BASIN. 



from the nearest railroad towns. At each of the lakes a boat was 

 secured and the whole of the lake shore and as much of the outlet as 

 was deemed advisable were examined. The fact that quite a portion 

 of the Yellow and Kanl^akee Kivers has been artificially dredged 

 and the old winding channel converted into a straight cross-country 

 ditch, presented changed conditions of extreme importance in their 

 relation to mussel propagation. These conditions have been accu- 

 rately recorded, and furnish an instructive contrast to the remainder 

 of the area worked. 



While the entire Kankakee Basin was thus more or less completely 

 examined and satisfactory results were obtained, the authors would 

 not regard the work as in any sense final. It is rather initiatory 

 and suggestive, and its value lies in the data and comparisons it 

 furnishes with reference to the natural conditions under which mus- 

 sels live and thrive in a region which has been as yet scarcely touched 

 by the progress of civilization. 



PHYSICAL FEATURES OF THE KANKAKEE BASIN. 



The Kankakee Basin embraces the whole of the northwest corner 

 of the State of Indiana south of the narrow Great Lakes drainage, 

 and adjacent portions of Illinois, and is drained by the Kankakee, 

 Yellow^, and Iroquois Eivers and their tributaries. These 3 rivers, 

 the principal streams that flow into them, and 12 of the more im- 

 portant lakes lying within the basin were thoroughly examined. 



This basin is radically different from that of the Maumee River, 

 previously examined, in that the Indiana portion of it lies wholly 

 within what geologists designate as a plain of accumulation.- The 

 origin of the valley can not be stated more concisely than in the 

 words of W. S. Blatchley in the Twenty-second Report of the Geol- 

 ogy of Indiana, page 59 : 



The valley doubtless owes its origin to the flow of waters which followed the 

 melting of one of the later retreating ice sheets. This flow was at first suflSi- 

 cient in volume and velocity to erode the present valley to quite a depth through 

 the underlying clay. Later, on account of a diminution of the supply of water, 

 as well as the gentleness of the slope, the current became too sluggish to erode 

 much deeper or to carry coarse material^ and only the finer sediment was 

 brought down. From a still further diminution of the water supply, as well as 

 by the building up of a sedimentary dam near the western end of the valley, 

 the water for a long period ceased to flow, and a lake of shallow depth resulted. 

 Again by a new accession of water from the northwest, the barrier at the foot 

 of the valley was washed away and the river of the present had its beginning. 

 At first its waters fiowed the full width of the valley, but in time their volume 

 decreased, and a portion of the river's bed became bare in summer. Over this 

 a vegetation sprang up and decayed. A soil was thus started above the sands 

 and was added to each year by the decay of the summer's vegetation and the 

 sediment brought down by the overflow in the spring. The main current of 

 the stream was thus gradually narrowed until it reached its present size. 



