120 



FISHES OF ILLINOIS 



ing males with the head jet-black, except for a light transverse bar at 

 back of opercle, the dorsal blotch enlarged and extending as a broad 

 bar from front to back of fin; other fins and entire body more or less 

 dusky. Head 4 to 4 . 4 in length, small, but rather broad and flat above; 

 the muzzle very blunt; width of head 1 . 6 to 1 . 8 in its length; interorbital 

 space 2.2 to 2. 5 ; eye 3 . 5 to 4 . 4 in head ; nose 3.1 to 3.4, longer than 

 eye; mouth small, inferior, nearly or wholly horizontal, the tip of the 

 upper lip below level of lower margin of orbit; maxillary scarcely longer 

 than eye, 3 . 8 to 4 . 3 in head , reaching to posterior nostril ; lower jaw in- 

 cluded; isthmus not quite so broad as in the last species, its width about 

 T V diameter of orbit. Teeth 4-4 ; intestine about twice the length of head 

 and body; peritoneum black. Dorsal fin 1-8 (rarely I 7), placed a little 

 behind ventrals and about equidistant between front of eye and base of 

 caudal ; longest dorsal ray 1 . 4 to 1 . 7 in head ; anal rays 7 ; pectorals short, 

 reaching little more than half way to ventrals, no difference- in this 

 respect being noticeable between males and females; ventrals in both 

 males and females falling short of vent. Scales 6 or 7, 41 to 44, 4, rather 

 crowded before dorsal, but not so much so as in the last species, rows 

 before dorsal about 23 ; lateral line usually complete, with a slight 

 ■downward curve in front of ventrals. 



Fig. 24 



This is by far the most abundant and widely distributed minnow 

 in Illinois. It appeared in 377 of our collections, ancl is abundant in 

 all of our river basins, in the glacial lakes of the northeastern part of 

 the state, and in the streams of the Lake basin. Generally speak- 

 ing, it ranges from W innipeg and Lake Champlain through the 

 Great Lake basin and the north Atlantic region as far as New Jersey, 

 and down the Mississippi Valley to the Alabama and the Rio Colo- 

 rado of Texas. It passes freely into the lower Illinoisan glaciation, 

 occurs abundantly in small streams along the bluffs of the Mississippi, 

 and seems to find a satisfactory place of residence in streams of any 

 size or lakes or ponds of any description. It is most abundant in 

 creeks (coefficient, 2.57), and scarcely less so in the smaller rivers 

 (2 . 03 ) , but is rather rare in the larger rivers, from which it has been 

 taken by us but 23 times in 293 collections. 



It is one of the mud-eating group, the alimentary canal being 

 commonly packed from end to end with mud containing filamentous 



