HADEOPTERUS BLACK-SIDED DARTEES 287 



length. Color of midsummer females and immature males yellowish olive 

 or straw, with dark blotches and mottlings; back with about 8 quadrate 

 spots, between which, on upper portion of sides, are dark, longitudinally 

 disposed marblings; a row of 7 or 8 large dark blotches along middle of side, 

 more or less confluent, and sometimes forming a continuous moniliform band, 

 their color dark bluish olive to bluish black; belly grayish in front, darkened 

 with smoky blue posteriorly; head dark olive, with a darker streak before 

 eye, and one below it, directed slightly backward; cheeks and opercles olive, 

 with sprinkling of iridescent coppery and emerald; pupil dead black; iris 

 brownish except for a faint narrow gold rim next to pupil; dorsal 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 isthmus, distance from tip of snout to angle and to back of 

 orbit about equal. Dorsal fin XIII-XV, 11-14; 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 notice- 

 ably emarginate; 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 

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

 embedded scales; breast naked; middle line of belly with enlarged caducous 

 plates; scales of body markedly ctenoid, giving this fish a more or less charac- 

 teristic feeling of roughness. 



This darter, of comparatively plain and somber colors, is 

 more abundant in Illinois than H. phoxocephalus, but is similarly 

 distributed, differing, however, in the fact that our collections, 

 168 in number, 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 com- 

 panion 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 distribu- 

 tion extending from Manitoba and the Great Lake region to 

 Arkansas. It is especially common in the Ohio Valley. East- 



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

 more or less broadly connected (e.g., 28187, Salt creek, Logan Co.). These specimens do not 

 have the small mouth and three caudal spots of H . scierus. 



