(49) 
The following table shows the position of the vent in 26 specimens. 
Length of 
Fish in Inches. 
Position of Vent. 
1 
Opposite middle of ventrals. 
1 
same. 
1 
same. 
1 
same. 
4 
u anterior two-fifths of ventrals. 
4 
“ anterior third “ 
il 
same. 
il 
same. 
il 
same. 
ii 
same. 
4 
Opposite anterior fourth of ventrals. 
14 
same. 
4 - 
Opposite middle of ventrals. 
4 
Just behind base of ventrals. 
2 
Between bases of ventrals' (as in type of U S. isolepis.”) 
21 
Between bases of ventrals. 
21 
same. 
3 
In front of ventrals, J- of the distances from base of 
ventrals to the throat “knob.” 
3 
distance to “knob,” (about as in types of “ A . 
mesotrema .”) 
31 
j- distance from ventrals to “knob.” 
H 
f distance to the “knob.” 
H 
f distance to the “knob.” 
4 
Half way from ventrals to “knob.” 
4 
4 distance to “knob,” (as in “A. cookianus ” and in 
A. say anus.) 
4 
1 distance to knob. 
4 
1 distance to knob. 
No other conclusion seems possible from the above except that the vent 
moves forward as the fish grows older, by the lengthening of the horizontal 
part of the intestine or “rectum” of the fish. Sternotremia isolepis is the 
young, Sternotremia mesotrema the half- grown and Aphododerus cookianus 
the adult of one and the same fish. 
Aphododerus isolepis occurs in sluggish waters and bayous throughout 
the state. I have seen specimens from Calumet River, from numerous 
streams and sloughs in the southern part of the state and from the Wabash 
River at Mount Carmel, — the latter'collected at different times by Robert 
Ridgway and Robert Kennicott. Union and Johnson counties. 
