VARIOUS KINDS OF UNIO SHELLS 77 



In Fig. 10 a Lampsilis rectus, or "black sand shell," is 

 shown, about one-third natural size. This variety is scat- 

 tered through most of our rivers, but is not especially 

 plentiful in very many of them. It is usually mixed 

 among other shells and not confined to colonies like some 

 of the other varieties. The size and shape of the black 

 sand shell is very much in its favor, but too often this 

 shell is colored pink or purple. When the nacre is white 

 it is valuable for both buttons and knife handles. Occa- 

 sionally some very valuable pearls are found in this va- 

 riety. 



The Lampsilis anodontoidcs, or "Slough sand-shell," 

 brings the highest price of all the fresh-water shells. It 

 is usually exported to be used in making novelties and 

 knife handles. This shell is shown in Fig. n, in about 

 one-third natural size. The yellow sand shell is com- 

 mon in most of our rivers and prefers to live in sandy 

 places. These shells are nearly always white and have a 

 pearly nacre. When pearls are found in them they also 

 have a high luster and good value. 



The Lampsilis fallaciosus, or "slough sand-shell," is 

 illustrated in Fig. 12, one-third natural size. It lives in 

 slow currents near muddy banks. This shell is often 

 loo small to be valuable, although the larger and thicker 

 ones are worth as much as the "yellow sand shells." 

 Some of the shells are very beautiful. Pearls are found 

 in this variety some times, but not often. 



Fig. 13 shows The Quadrula undulata, or "three ridge," 

 one-third natural size. This variety is very .common in 

 the Illinois River, and other deep rivers. It is a good 



