324 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



sale and reckless destruction of the shells over large areas; the total lack of system 

 in the search for pearls, as contrasted with the methods that have been developed on 

 a smaller but far more profitable scale in Europe, all seemed to call for a careful 

 investigation by the Commission, with a view to better knowledge and wiser direction 

 in the matter of inland American pearl fisheries. 



Undoubtedly, for a considerable period after the first explorations, the pearl 

 resources of North America seem to have attracted little attention. The Indian race 

 was contending with the whites for the possession of the country; it was a time of 

 uncertainty and strife for both races; and not until the great waterways of the 

 Mississippi Valley had been won by the whites, the region occupied, and settled com- 

 munities established, do we again begin to find any indications of the search for fresh- 

 water pearls. For some two centuries the Unios lived and multiplied in the rivers 

 and streams unmolested by either the native tribes that had used them for food, or 

 the pioneers of the new race that had not yet learned of their hidden treasures of 

 pearl. 



It is with some surprise that one notes that so few American couchologists have 

 paid attention to our native pearls. It is probably accounted for by the fact that the 

 pearls are contained in old, distorted, and diseased shells, which are not so desirable 

 for collections as the finer specimens. Collectors who have opened many thousands 

 of Unios have never observed a pearl of value. Pearls are usually found either by 

 farmers, who devote their spare time to this industry, and if no result is obtained 

 suffer no loss, or by persons in country villages who are without regular occupation, 

 but are ever seeking means for rapid increase of fortune. Multitudes of shells that 

 do not contain pearls are destroyed in the search. 



HABITAT OF THE FRESH-WATER MUSSELS. 



From the many inquiries sent out, the general indications from the answers are 

 quite plain, to the effect that the shells are chiefly found in rather rapid streams, in 

 which the bottom would naturally be sandy or gravelly and the water clear. Other 

 species, however, occur on muddy or clayey bottoms, where the current is slower. 

 The references to rock bottom do not concern so much the immediate surface where 

 the shells are found, as the underlying bed on which the softer materials rest. 

 In the matter of depth, also, the large preponderance of answers in favor of shallow 

 streams may mean, not so much that the Unios greatly prefer shallow water, as that 

 they are more readily found and gathered there. The frequent allusions to ''hard" 

 or calcareous water seem to confirm the general impression that streams of this kind 

 are favorable to the development of mollusoan shells, both in size and in abundance, 

 and the greater proportion of calcareous matter in the water tends to induce the 

 prolific secretion of the pearls. 



A Florida writer states that the best Qnio growth is found in lakes with outlets, 

 the water pure and fresh; but adds that it is sometimes sulphurous. A Texas pearler 

 (Colorado, Concho, San Saba, and Llano rivers) refers to the water as becoming 

 slightly alkaline in dry times; and another Texas pearler (Colorado and Llano) makes 

 a similar statement. A New York pearler (De (irasse River and Plum Brook) men- 

 tions the water as brown or black the clear, brown water of the hemlock districts, 

 familiar in northern Xew York. 



The general conclusions most clearly brought out may perhaps be summed up 

 as follows: The shells are most abundant in swift and clear water where the bottom 



