22 MUSSELS OF CUMBERLAND RIVER AND TRIBUTARIES. 



very different. Such a similarity is found in Roaring and Rock 

 Castle Rivers, although the locahties are widely separated and the 

 surrounding country quite different. 



4. Some species demand peculiar conditions, and their presence 

 or abundance in any locaUty depends on the presence and extent of 

 the favorable conditions. 



The washboard {Q. Jieros) lives in holes or depressions in the bottom, 

 full of soft mud. Any mussel bed in the Cumberland that has such 

 holes will be Ukely to contain washboards, whether that bed is high 

 up the river or low down toward the mouth, and the percentage of 

 the washboards will depend on the area covered with such holes. 



5. The Cumberland is very different from the Maumee and Kan- 

 kakee Rivers in that it shows a marked differentiation between small 

 and large stream species, between the main river and its tributaries, 

 but there is very Uttle evidence of migration along the main river 

 itself. 



Such species as are confined to the upper, middle, or lower portions 

 of the river owe their habitat chiefly to the fact that here, as else- 

 where, they frequent smaller or larger streams, as the case may be. 



Accordingly, we may distinguish the following classes: 



(a) Small-stream species restricted to the upper portions of the 

 river and its tributaries. Here belong seven species. Anodontoides 

 ferussacianus was found only in the tributaries and not at all in the 

 main river. The other six species, Lampsilis perdix, multiradiata, 

 orhiculata, and punctata, and Alasmidonta minor and truncata are 

 distributed in various tributaries and in the main river both above 

 and below the falls. None of these are commercial species. 



(6) Large-stream species, restricted to the lower portions of the 

 main river. There are nine of these species, seven of which are not 

 found in any of the tributaries, viz: Lampsilis ventricosa and f alia ciosa, 

 Ohovaria retusa and ellipsis, and Quadrula heros, ebena, and fragosa. 

 The other two species, Lampsilis anodontoides and Quadrula undata, 

 were found in Harpeth River and the former also in Red River a« 

 well as in the main Cumberland. The most of these large-stream 

 species are good button shells, as would be expected. Indeed, the 

 only exception is Ohovaria retusa, which is the smallest of them all and 

 for that reason the least valuable. 



(c) Species of universal distribution, which are well scattered 

 throughout the entire length of the main river. There are seven of 

 these species, three of which, the Ohio River pigtoe (Quadrula 

 ohliqua), the pink warty-back (Q. tuherculata) , and the butterfly 

 (Plagiola securis), are not found in any tributary. The other four 

 are the southern mucket {Lampsilis ligamentina gibha), the pocket- 

 book {L. ovata), the spike {Unio gihhosus), and the elephant-ear 



