84 PEARLS AND PEARLING 



grows sparingly in both lakes and rivers, and is known 

 throughout most of the States. In some instances the 

 shell is too thin for button material, but usually it is a 

 good shell for the purpose. The nacre is generally white 

 and lustrous, although some times a few pink ones are 

 found. They are some times used in the manufacture of 

 pocketbooks and novelties. Slugs, baroques and pearls 

 are occasionally found in these shells. 



The Symphonota complanata, or "razor-back," or 

 "hatchet-back," or "heel-splitter," or "hackle-back," is 

 shown in Fig. 20, about one-third natural size. This va- 

 riety is common in most rivers, but is not a valuable shell, 

 unless it is thick and has a white nacre. As a rule, how- 

 ever, the shells are thin and colored. They do not grow 

 in beds by themselves, but are usually scattered among 

 other varieties of shells. Pearls are not often found in 

 the "razor-backs," but when they are found in these 

 shells they are very brilliant and valuable. 



The Quadrula obllqua, or "pig-toe," is shown in Fig. 

 21, one-third natural size. This shell is white, with a 

 good luster and is a good shell for making small but- 

 tons. It is a very common variety and in some rivers they 

 are very plentiful. Its small size reduces its value some- 

 what as a button shell. Occasionally nice small pearls 

 are found in the "pig-toes." 



The Quadrula metanewa, or "monkey- face," is illus- 

 trated in Fig. 22, one-third natural size. This shell also 

 has a pearly white nacre, but is small and for that reason 

 is not quite so valuable as many larger shells. It has 



