282 FISHES OF ILLINOIS 



its greatest depth; depth of caudal peduncle 2.6 to 2.9 in its length. 

 Color olive-buff to yellowish ; sides of adults crossed by from 30 to 40 bars 

 of dark green color, varying* in width and in extent from above downward, 

 the most usual arrangement being an alternation of short and narrow with 

 wider and longer ones, the merging of bars producing in some older 

 specimens a more or less reticulated pattern on the sides and forming 

 on the back 3 or 4 large saddle-like blotches; fewer bars (IS to 30) in 

 younger specimens, the intermediate narrower and shorter ones being 

 faint or entirely absent in the very young; a small but prominent 

 black spot at base of caudal fin, encircled by a band of yellow; snov/t 

 dusky; cheeks with iridescent green, blue, and yellow; iris with golden 

 margin; dorsal and caudal fins barred, other fins plain. Head 3 . 9 to 



4.3 in length, long and pointed; width of head 1.9 to 2.2; interorbital 

 space flat or slightly concave, 4 to 4.8 in head; eye high, obliquely set, 

 its long diameter 3.6 to 4.2 in head; snout long, conic, with a pad at 

 its tip, 2.8 to 3.3 in head; mouth small, inferior, overhung by the pig- 

 like snout, maxillary reaching scarcely to posterior nostril-opening; cleft 



3.4 to 4 in head; lower jaw much shorter than upper; gill-membranes 

 narrowly connected, distance from tip of snout to their angle scarcely 

 greater than to back of orbit. Dorsal fin XII-15; spinous and soft 

 portions usually very little separated, or not at all; height of first dorsal 

 2 to 2 . 3 in head, of second 1 . 6 to 2.2 (height of first 74 to 94 per cent, 

 of second) ; caudal truncate; anal II, 10-11; pectorals 1.2 to 1.4 in 

 head ; separation of ventrals about equal to their width at base. Scales 

 9-11, 83-93, 12-14; lateral line usually complete, as many as 1 to 6 pores, 

 occasionally lacking; cheeks and opercles fully scaled; nape of typical 

 specimens fully scaledf ; breast naked; belly with deeply embedded scales 

 and a median row of rather small pectinate caducous plates. 



Sexual differences not marked. The majority of our specimens are 

 young, and no gravid females appear among them. Testes were large 

 and white in males taken on the 12th of June 1901. 



This darter is distributed throughout the state from Cairo to 

 South Chicago and the northeastern glacial lakes, mainly, however, 

 in the larger streams. We have found it relatively most abundant 

 in medium-sized rivers, and next so in creeks, its frequency coeffi- 

 cients for such streams, as represented by our seventy collections of 

 the species, being 2 . 26 and 1 . 6 respectively. In the larger rivers, 

 on the other hand, and in lakes, ponds, and sloughs, it is much less 

 common, its ratio for each being .58. It is decidedly more frequent 

 in northern Illinois than in either central or southern. It, is not par- 

 ticularly choice of localities, and enters freely the turbid waters of the 

 lower Illinoisan glaciation. It has been taken several times along 



*For an interesting paper on variation in the color pattern of this species see 

 W. J. Moenkhaus, Amer. Nat., Vol. 28, pp. 641-660. 



fNaked in var. zebra Agassiz (Jordan and Evermann, Bull. U. S. Nat. Mus., No. 

 47, 1., p. 1027). Some apparent specimens of that form were taken in Illinois in early- 

 collections by the senior author. 



