16 



MUSSEL FAUNA OF THE KANKAKEE BASIN. 



algae around the siphonal (upper) end of the shell. These would be 

 a manifest aid in oxygenating the stagnant water in which the 

 mussels live, and might also be of assistance in keeping them on 

 top of the mud, just as webs of gossamer keep spiders suspended 

 high in air and enable them to perform aerial journeys. 



Of the mussels found luteolus was far the most common; then 

 came ventHcosus^ undulata^ and rectus^ in the order named. Many 

 of the luteolus and ventricosus and one ruhiginosa were gravid. 

 Atax ypsilophomis was found in nearly all the species and was espe- 

 cially common in luteolus^ ventmcosus^ and edentulus^ and many of 

 the eggs and 3^oung were found in the mantle. All of the rectus 

 shells had a deep pink nacre, as did also one ventricosus and one 

 ligamentinus. Both of the imhecillis found were gravid and were 

 imbedded perpendicularly in the mud, with the siphons pointing 

 straight upward, a very unusual position for that species. 



The minnows and darters were abundant on the mussel beds, as is 

 shown by the list of those obtained. Notropis blennius and Bole- 

 osoma nigrum were most in evidence and could be found every- 

 where, while the others were more scattered. 



Only a few mussels were collected below Knox, and they have 

 been recorded with the others from the old river channel. With 

 the account of the Twin Lakes which follows, this concludes the 

 investigations on the Yellow River. 



Station C. The Twin Lakes. — These "twins" are really four in 

 number, grouped near the center of the western third of Marshall 

 County in two pairs, separated by the Vandalia Railroad. The 

 eastern pair are elongated in a northwest and southeast direction and 

 lie in the same straight line. The eastern and smaller one is Lorance 

 Lake, about 80 rods in length and width. It is separated from the 

 larger lake b}^ a stream 50 rods in length. The larger is called 

 Meyer's or East Lake and is a mile in length and about 40 rods 

 wide. The western pair on the other side of the railroad are elon- 

 gated at right angles to the others, or in a northeast and southwest 

 direction, and they lie side by side with their long diameters parallel. 

 The northern, larger one is Cook or Northwest Lake, and is the 

 same size as Meyer's. The southern one is Holem or Southwest 

 Lake and is about three-quarters of a mile long and 30 rods wide. 

 It is separated from Cook Lake by a narrow ridge of gravel, 15 to 

 20 feet high and 200 to 300 feet in width. 



Lorance Lake empties into Meyer's through the short brook men- 

 tioned. Meyer's runs under the Vandalia Railroad track into Cook ; 

 Holem also drains into Cook from its southwestern end and Cook 

 delivers the drainage of all four lakes into Eagle Creek, which 

 empties into the Yellow River just above Knox. All the lakes are 

 very shallow, the maximum depth being under 20 feet, and the area 



