FRESH-WATER MUSSELS AND MUSSEL INDUSTRIES. 33 



MISCELLANEOUS GROUPS. 



There remain for brief mention about a dozen species which have Httle in common. 

 None is very numerous, generally speaking, but all are more or less familiar to fishermen 

 and manufacturers, while nearly all enter to some extent into button manufacture, 

 although they are rarely bought intentionally. Some, at least, have certain good 

 qualities. 



BULLHEAD GROUP. 



The bullhead, Pleurobema cesopus (Green) (PL XX), is a yellow-back, thick, knobby 

 shell, with nacre of excellent whiteness and luster. It is, however, exceedingly hard in 

 texture, difficult, therefore, to cut, and injurious to the saws. After the blank is cut, 

 the button is finished readily and takes a good polish. The fishermen in some locali- 

 ties have facetiously dubbed» this shell the ''clear profit," because it can be thrown in 

 to add weight at a profit to themselves and, supposedly, at a loss to the buyer. Sheep- 

 nose is another name, referring to its form. It is a mussel of rather wide distribution 

 in the Ohio drainage and eastern part of the Mississippi Basin northward. 



The fan-shell, or ringed warty-back, Cyprogenia irrorata (Lea) (PL XX), is a smaller 

 and flatter mussel of good form and appearance, but its qualities are reported to be sim- 

 ilar to those of the bullhead. It occurs in the Ohio drainage, especially Tennessee and 

 Kentucky. 



The dromedary mussel, Dromus dromas (Lea) (PI. XX), is somewhat like the 

 fan-shell, but without the low protuberances on the back of that shell. It is found in 

 the Tennessee and Cumberland River systems. In appearance it suggests the southern 

 mucket, but its qualities, so far as known, correspond to those of the fan-shell. 



The kidney-shell, Ptychobranchus phaseolus (Hildreth) (PI. XXI), is a much 

 more elongate shell, with hard nacre and an undesirable steely luster. It is found 

 in the Ohio drainage and is reported to extend northward to Michigan and southwest- 

 ward to Louisiana, Arkansas, and Kansas. 



HEEL-SPLITTER GROUP. 



The white heel-splitter, or pancake, Symphynota complanata (Barnes) (PI. XXII), 

 is of wide .distribution in the upper Mississippi and Ohio drainages, the upper St. Law- 

 rence drainage, and the Mackenzie River. It has a large, fine surface, but unfortunately, 

 the shell is nearly always thin. In some localities it becomes very large and of suitable 

 thickness but is brittle. The buttons can be finished with good luster, but the shell 

 is liable to split into pieces when the blanks are being cut. It is said that they can be 

 cut readily when fresh from the river and before the sheU has so dried out as to be 

 checking and splitting. 



In some places the name elephant's ear is applied to this species. The name is 

 appropriate enough, except that it has already been so generally applied to another 

 species to be discussed later. 



The fluted shell, Symphynota costata (Rafinesque), a comparatively thin-shelled 

 mussel of wide distribution, has recently come into use from certain streams in 

 Wisconsin. 



