66 
The Food of the Smaller Fresh- Water Fishes. 
under the genus and sometimes under the special group to which 
the genus is assigned. 
FAMILY APHREDODERIDAL 
This family is represented by a single peculiar species ( Aphre - 
doderus sayanus ), resembling the sun-fishes in most of its char- 
acters, but remarkably distinguished by the fact that the vent, 
although occupying the normal position in the young, opens in 
the adult far forward under the head, moving gradually to the 
front with increasing size. This fish is not over three inches in 
length. It occurs in rivers and smaller streams, as well as in lakes 
and ponds throughout the State. We have collected it from the 
Illinois River and various tributaries, as well as from the lakes 
connected with that stream, and from ponds and creeks through- 
out Southern Illinois. It has also been taken in the Calumet 
River near Chicago, and from lakes in that vicinity, but is not 
known to occur in Lake Michigan. It is said to be nocturnal in 
its habits, by Dr. C. C. Abbott, who kept specimens in an aqua- 
rium for some time.* The same author reports that in confine- 
ment it feeds voraciously upon small fishes, especially immature 
Cyprinidse; and for this reason he bestowed upon it the name of 
pirate perch , by which it has become generally known among 
ichthyologists. The observations presently to be detailed will 
show, however, that his specimens were doubtless forced to feed 
so largely upon fishes for want of food more natural to them, 
since in their native haunts fishes make but a small percentage of 
their ordinary food. 
The intestine of this species is short and simple, less than the 
length of the head and body without the tail, and distinguished 
only by the character previously mentioned. The gill apparatus 
is ineffective, the rakers being very short, thick, blunt, and few, 
and covered with short spinules. The pharyngeal jaws consist 
of small plates, covered with short, sharp spinulose teeth, similar 
to those of the sun-fishes. The mouth is large, but not remarka- 
bly protractile. 
The specimens dissected number nineteen, representing seven 
different dates and localities, throughout Central and Southern 
Illinois. Some were taken from small temporary ponds left by 
*Proc. Phil. Acad. Nat. Sci., 1861, p. 95. 
