144 FISHES OF ILLINOIS 



greater thickness at the nape, the more elevated back and steeper profile, 

 and by the absence, in most specimens, of the black spot on the posterior part 

 of the dorsal fin. Length 2^ 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 

 iridescent 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 postopercular 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, the 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, 

 nearly twice the small eye; 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, usually 4-4, though 

 0, 4-4, 1, 1,4-4, 0, and 1,4-4, 1 are not uncommonly met with in our collec- 

 tions; 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 usually 8, sometimes 7 or 9; pectorals % to ventrals, 1.2 to 1.4 in 

 head; ventrals to vent in females, to front of anal in males. Scales 6, 34-37, 

 3-4; rows before dorsal 14 to 17; lateral line complete, strongly decurved, 

 being approximately 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 

 of 1.69, and it enters the lower Illinoisan glaciation in the 

 branches of the Big Muddy. It is closely allied to N. whipplii, 

 and appears, in fact, to intergrade with that species, of which 

 it is the representative to the south and west. 



