MUSSEL FAUNA OF THE KANKAKEE BASIN. 43 



is usually a smaller shell and has a more distinct posterior ridge, 

 which is the chief distinguishing characteristic. The nacre is never 

 pink, but may in rare instances have a yellowish cast. The species 

 has about the same value for buttons as Q. coccinea. In the button 

 makers' category it would be classed with the pig-toe group, but it 

 has received no regular trade name. 



Q. ruhig'mosa was found almost the entire length of the Yellow 

 and Kankakee Basins, but was more common in the lower river. 

 It was common in the clammer's shell pile at Momence and in the 

 Iroquois. It is one of the few Quadriilas found fairly common in 

 the lakes. We found it in both Tippecanoe and Koontz Lakes. In 

 lakes it is represented by a peculiar dwarfed form with a satiny 

 epidermis. It was difficult to distinguish between the peculiar in- 

 flated form found at L'Erable and trigona. Some of these were 

 gravid, all four gills being filled, and of a reddish color. The flesh 

 of some of the examples was wliite, of others reddish. Distomid 

 cysts were very abundant in the margins of the mantle. 



6. Quadrula pustulosa {Lea). Warty-hack. — This is a well-known 

 shell among the clammers and button cutters. It is exceedingly 

 variable, sometimes being small and much inflated, and at other 

 places flattish. In some localities it is exceedingly rough and warty 

 and in other places almost smooth. It therefore varies considerably 

 in value, the flatter shells being of more value than the inflated 

 and the smooth better than the rough. In the Kankakee Basin this 

 species has about the same distribution as Q. ruhig'mosa^ but is never 

 found in lakes, and is more common in the lower stretches of the 

 river. The examples obtained at Nickelplate were unusually flat- 

 tish; those about Momence had some of the tubercles developed 

 into long ribs elongate along the lines of growth. It was common 

 in the clammer's pile at Momence and at the pearler's camp below 

 Momence. It was also found in the Iroquois at Watseka and 

 L'Erable. 



7. Quadrula lachrymosa {Lea). Maple-leaf. — This is a well-known 

 shell among button manufacturers, hardly so much on account of its 

 excellence as of the fact that it occurs in considerable abundance 

 in regions where clamming is carried on and the shells can be made 

 good use of. In quality they are about the same as Q. pustulosa^ 

 the warty-back, but the sulcus or groove along the middle of the 

 shell prevents it from being used to so good an advantage. 



In the Kankakee Basin this species is found only in the lower 

 stretches of the Kankakee River and in the Iroquois, and then only 

 in small numbers. At L'Erable on the Iroquois (Aug. 21) they were 

 beginning to become gravid. 



8. Quadrula metanevra {Ra-finesque) . Monkey-face. — ^This species, 

 which has about the same commercial value as the preceding, was 



