FRESH-WATER MUSSELS AND MUSSEL INDUSTRIES. 33 
MISCELLANEOUS GROUPS. 
There remain for brief mention about a dozen species which have little 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 esopus (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), isa 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) (Pl. 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) (Pl. 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) (Pl. 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 shell 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. 
