THE PEARLY FRESH-WATER MUSSELS OF THE UNPrE.D STATES; THEIR 
HABITS, ENEMIES, AND DISEASES, WITH SUGGESTIONS FOR THEIR 
PROTECTION. 
By CHARLES T. SIMPSON. 
The J^aiades, or pearly fresh water mussels, have a distribution throughout the 
lakes and streams of the globe, not only on the continents, bnt also on all the larger 
and some of the smaller islands. They exist in countless numbers, especially in the 
LTnited States, which seems to be the metropolis of these forms, both as to species and 
individuals. Probably over 600 valid species are now living in North America, and 
fully three-fourths of these are found in the Mississippi drainage area and the streams 
which fall into the Gulf of Mexico from the north. Many of these mussels here attain 
a great size. Some are covered with knobs or pustules, or have peculiar and striking- 
forms, while others are brilliant with radiating stripes or beautiful and intricate 
patterns of coloring. The interiors of many of these species are very rich, the colors 
varying from almost blackish-purple to coppery, glowing red, pink, salmon, straw- 
color, and silvery white. 
Within the past few years a great deal of interest has been aroused in the United 
States in regard to these mussels. Thousands of persons have given more or less 
attention to hunting them for their pearls, which often have a high money value, and 
others have gone quite extensively into the business of manufacturing the shells into 
buttons and various ornaments. So great has been the drain on them that in many 
places they have become very scarce, and are even threatened with extinction. Mr. 
George F. Kunz, the well-known gem and pearl expert, has just published a paper on 
the fresh-water pearls and pearl fisheries,* containing an immense amount of useful 
and accurate information. In the present paper the subject of the pearly mussels will 
be treated more from a biological standpoint. 
The species inhabiting the Mississippi drainage area extend their range on the 
south through all the streams of the United States flowing into the Gulf of Mexico, 
and to some extent into Mexico; on the north some of them range nearly to the Arctic 
Ocean, and from the Eocky Mountains, which are a barrier on the west, throughout a 
considerable part of the St. Lawrence drainage area. On the Atlantic coast from the 
St. Lawrence to the Gulf of Mexico the streams and lakes are filled with mussels, usually 
simple in form and dull in color and quite different from those of the Mississippi 
region. Only a very few species are found in the waters draining into the Pacific. 
The shells of the pearly mussels consist of two convex valves, which fit together 
and inclose the animals. These valves are covered with a coating of somewhat 
leathery matter called the epidermis, and are joined together at the upper part or 
back of the animal by a hard, horny, rather tough and elongated C spring, which 
has a tendency to throw them open. In front of this spring, which is called the 
ligament, there are found, on uninjured shells, a couple of slightly corrugated eleva- 
*“The fresh-water pearls and pearl Hsheries of the United States,” U. S. Eish Coininission 
Bulletin for 1897, pp. 373-426, pis. i-xxii. 
279 
