MUSSELS OF CUMBERLAND RIVER AND TRIBUTARIES. 23 



{V. crassidens). The last two, of course, are culls, but all the others 

 are valuable commercial shells. 



(d) Species confined to restricted areas, including all of the rare 

 forms that are of interest chiefly to the conchologist. These include 

 all of the Truncillas, which were found in places widely separated from 

 one another, and one of which was new to science; nine species of 

 Lampsilis — tseniata, picta, lienosa, vanuxemensis, trabalis, parva, glans, 

 Isevissima, and leptodon — all of which are too small or too thin-shelled 

 to be of any value. Drornus caperatus and Symphynota complanata; 

 two Anodontas, imhecillis and grandis; two Pleurobemas, clava and 

 crudum; and four Quadrulas, undulata, tuberosa, rubiginosa, and 

 granifera. These last four have some commercial value but not very 

 much. 



6. The great bulk of the mussel fauna of the river is thus made up 

 of the seven universally distributed species, and two of the large 

 stream mussels — Quadrula heros and Q. ehena. All the others are 

 confined to such restricted areas or occur in such small numbers as to 

 possess only an incidental or accessory value. 



NOTES ON THE VARIOUS STATIONS. 

 THE UPPER RIVER AND ITS TRIBUTARIES. 



This portion of the river was examined by Mr. Boepple in 1910 as 

 well as by the present party in 1911. Both the river and its tribu- 

 taries are rather swift mountain streams which are much used as a 

 source of power to run small gristmills, and hence they are fre- 

 quently interrupted by dams. The bottom is mostly bedrock 

 sandstone, with occasional fissures and sand and gravel pockets and 

 bars, the latter furnishing the only locahties where mussels can hve. 

 Consequently the shells are very few in number and widely scattered. 

 The Clear Fork has more sand bars and pockets than the main river, 

 and hence considerably more mussels. 



Mr. Boepple in his notes called attention to the apparent presence 

 of acids in the water above the great falls, which quickly dissolved the 

 nacre of dead shells, and the present party observed the same thing. 

 Moreover, in the small beds above the falls the muskrats had made 

 considerable inroads into the mussel fauna. Against so many 

 unfavorable conditions the mussels fiiid it very hard to hold their 

 own, and the few species able to survive are not of any importance 

 either to the pearlers or the button manufacturers. These mussels 

 above the falls are not only thin-sheUed but are much dwarfed, and 

 Unio gihhosus, the most common species, has a very pale nacre, which 

 frequently becomes white or yellowish and approaches closely a 

 dwarfed form found in Green River, Ky. 



