120 FISHES OF ILLINOIS 



lines crossing dorsal and caudal; breeding 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 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 included; 

 isthmus not quite so broad as in the last species, its width about /io diameter 

 of orbit. Teeth 4-4; intestine about twice the length of head and body; 

 peritoneum black. Dorsal fin 1-8 (rarely 1-7), 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, and 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 speaking, it ranges from Winnipeg 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 Colorado 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 fila- 



