46 MUSSEL FAXJNA OF THE KANKAKEE BASIN 



15. Symphynota conhplanata {Barnes), Heel-splitter^ hatchet- 

 hack. — At its very best, this species, offering a broad, flat expanse of 

 satiny wkite nacre, is an excellent button shell, furnishing more 

 blanks per shell than any other species. In many cases, however, it 

 is too thin for use. This species is found only in the lower half of 

 the river; the first seen w^ere at Hebron Bridge, where we found three. 

 In the clammer's shell pile at Momence it was common and large. 

 It was also found at the mouth of the Iroquois, some fine ones were 

 seen at Kankakee, 111., and a few at Wilmington. Small ones, 

 cleaned out by muskrats, were found in Mazon Creek. 



16. Symphynota costata {Raflnesque) . Squaw-foot. — This species 

 is rarely used for buttons, the nacre being too yellow, and frequently 

 too thin. It is well distributed throughout both the Yellow and Kan- 

 kakee Rivers, and is fairly common at Plymouth below the dam ; 2G 

 were obtained there in a shell pile left by pearlers. In the clammer's 

 pile at Momence it w^as common and large, although not so innnense 

 and thick as found in some rivers. It was also found in the Iroquois 

 Kiver at L'Erable. This species in some rivers is especially subject 

 to distomid infection and occasionally bears pearls. 



17. Symphynota compressa {Lea). — Compared with the Symphy- 

 notas just mentioned, this is a small shell. It is always too thin to 

 have any commercial value. It was found in the Yellow Eiver from 

 Plymouth just below the dam to the Zinc Bridge at Ober, in Potato 

 Creek at Walkerton, in Yellowbanks Creek, and the Kankakee at 

 Davis. It is a species belonging to small streams. It was beginning 

 to be gravid at Plymouth September 20, with the embryos orange red, 

 in the outer gills of the parent. 



18. Anodontoides ferussaclanus {Lea). — This is a small thin shell 

 of no economic importance. Like Symphynota compressa it is 

 usually confined to small streams, and occasionally lakes. It was 

 rather common at Plymouth; one was found dead in Lake of the 

 AVoods, and a few in Yellowbanks Creek. The form found in this 

 area appears to be the subspecies subcylindraceus. 



19. A7iodonta grandis {Say). — This species, although it reaches 

 large size, is usually thin-shelled, and only exceptionally attains 

 sufficient thickness to have any commercial value. It was found 

 at the majority of stations throughout the Yellow and Kan- 

 kakee Rivers, and in the Iroquois. In the lakes (except Fish Lakes, 

 where the river form occurred) this species was represented by a' 

 dwarfed somewhat inflated form, the variety footiana. Particular 

 attention was paid to the shells above the dam at Plymouth, where 

 the water had been pond-like or lake-like for many years, to observe 

 whether the shells were beginning to approximate in appearance the 

 dwarfed form of the neighboring lakes; but they were all the large, 

 elongate river form. 



