144 FISHES OF ILLINOIS 



adult, by the greater thickness at the nape, the more elevated back and 

 steeper profile, and by the absence, in most specimens, ol the black spot 

 on the posterior part of the dorsal fin. Length 2f inches; depth 

 2.7 to 3.2 in length in adults, the young more slender; caudal 

 peduncle shorter than head, its depth 1.7 to 2.1 in its length. 

 Color of females and postnuptial males olivaceous under irides- 

 cent steel above, pale greenish to greenish gray and silvery lower, down 

 and on belly; a faint purplish wedge-shaped bar behind opercles; fins 

 plain (in typical specimens), tinged with reddish or orange in males. 

 Spring males with the upper parts a brilliant iridescent steel-blue, the 

 sides and belly orange-red to crimson, and the top of head, cheeks, and 

 opercles flushed with rose; gill-opening bordered with red; the postoper- 

 cular bar a brilliant purplish violet, behind which is a broad vertical band 

 of faint crimson; all the fins reddish, the dorsal dusky with greenish at 

 base; pectorals plain red; ventrals blood-red tipped with a narrow margin 

 of orange; caudal dusky near base, crimson outward, tipped with darker. 

 Head 3 . 6 to 4 in length, stout and deep, depressed but not flat above, 

 1 lir profile angled at the nape, most so in males; width of head 1 . 8 to 2 . 2 

 in its length; interorbital space 2.5 to 2.8, nearlv twice the small eve; 

 eye 4 to 4.5, less than nose; nose 3.1 to 3 . 6 in head, conic, sharper and 

 upturned in males; mouth oblique, the tip of upper lip above level of 

 lower margin of pupil; maxillary 3 to 3 . 6 in head, reaching to vertical 

 from back of posterior nostril, but not to orbit; lower jaw included, the 

 upper considerably projecting in males (in females the jaws are usually 

 very nearly equal) ; isthmus less than pupil. Teeth variable, usuallv 4-4, 

 though 0, 4-4, 1.1, 4-4, 0, and 1, 4-4, 1 are not uncommonly met with 

 in our collections; the supernumerary teeth are usually weak and much 

 less developed than in the next species, in which the number is normally 

 1, 4-4, 1; intestine shorter than head and body, in which it is contained 

 .8 to .9 times; peritoneum silvery, finely but not densely specked with 

 black. Dorsal fin with 8 rays, set a little behind or over the ventrals; 

 longest dorsal ray 1 . 1 to 1.3 in head; anal rays usuallv 8, sometimes 7 or 

 9; pectorals 3 to ventrals, 1 .2 to 1 .4 in head; ventrals to vent in females, 

 to front of anal in males. Scales 6, 34-3 7, 3-4; rows before dorsal 14 to 

 17 ; lateral line complete, strongly decurved, being approximatelv parallel 

 with the lower outline. 



This little. redfin, one of the most beautiful, in its breeding 

 colors, of any of our minnows, is essentially a western species; 

 and all our 163 collections have been made from the streams 

 of the Mississippi drainage. Outside this state the species ranges 

 from South Dakota and Wyoming to Nebraska, Kansas, Missouri, 

 and Arkansas, and the tributaries of the Rio Grande. It is a 

 minnow of the .streams, present in about equal ratio in creeks and 

 the larger and the smaller rivers, but found in lowland lakes with 

 only about half the frequency of its occurrence in running waters. 

 It tolerates muddy waters, as is shown by its frequency coefficient 

 ot 1.69, and it enters the lower Illinoisan glaciation in the branches 



