HADROPTERUS BLACK-SIDED DARTERS 287 



it, directed slightly backward; cheeks and opercles olive, with sprin- 

 kling of iridescent coppery and emerald; pupil dead black; iris brownish 

 except for a faint narrow gold rim next to pupil; dorsals and caudal 

 plainly, pectorals faintly, barred. Adult males in breeding color with 

 entire body more or less smoky or dusky, lacking the contrast between 

 blotches and interspaces seen in females; in all adult males the spinous 

 dorsal crossed near its base by a broad dark band and both the caudal 

 and anal dusky. Head pointed, 3.8 to 4 in length; width of head 

 1 . 8 to 2 .2 in its length; interorbital space flat, narrow, about § of eye, 

 5.5 to 6.7 in head; eye nearly round, 3.4 to 4 in head; nose bluntly 

 pointed, 3 . 6 to 4. 1 in head; mouth rather large, the maxillary extending 

 past front of orbit, the cleft 3 to 3 . 4 in head ; lower jaw very little shorter 

 than upper; gill-membranes as a rule not noticeably connected* at isth- 

 mus, distance from tip of snout to angle and to back of orbit about equaL 

 Dorsal fin XIII-XV, 1 1-14; spinous and soft portions as a rule distinctly 

 separated at base; height of first dorsal 1 . 9 to 2 . 3 in head, of second 1 . 7 

 to 2 (height of first 82 to 94 per cent, of second) ; caudal noticeably emar- 

 ginate; anal II, 8-11 ; pectorals 1 . 1 to 1 .3 in head; separation of ventrals- 

 about equal to their width at base. Scales 8-10, 64-70, 9-11; lateral 

 line nearly straight, usually complete, one or two pores sometimes lack- 

 ing; cheeks and opercles covered with small scales; nape naked or with 

 embedded scales; breast naked; middle line of belly with enlarged cadu- 

 cous plates; scales of body markedly ctenoid, giving this fish a more or 

 less characteristic feeling of roughness. 



This darter, of comparatively plain and somber colors, is more 

 abundant in Illinois than H. phoxocephalus, but is similarly distrib- 

 uted, differing, however, in the fact that our collections, 168 in num- 

 ber, have come much more generally from the eastern part of the 

 state than from the western, and that it does not occur so frequently 

 as phoxocephalus in the larger rivers. It is about equally abundant in 

 the smaller rivers and in creeks, but rarely occurs in the larger rivers 

 or in bottom-land lakes and ponds. In ecological relations it also 

 closely resembles its companion species of the genus, but seemingly 

 has a less decided preference for a rapid current or a clean bottom. 



It ranges somewhat farther northward, its area of distribution 

 extending from Manitoba and the Great Lake region to Arkansas. 

 It is especially common in the Ohio Valley. Eastward it is reported 

 from the James and the Roanoke, w^estward from Kansas to Dakota, 

 and northward from Winnipeg and the Assiniboin. 



In'our studies of its food we were not able to distinguish any dif- 

 ferences between this and the related species, and the two have, 

 indeed, occurred together in our collections one and a half times as 

 frequently as is the average for the family. 



*In occasional collections of this species we meet with specimens with gill-mem- 

 branes more or less broadly connected (e. g., 28187, Salt creek, Logan Co.). These 

 specimens do not have the small niovith and three caudal spots of H. scierus. 



