HYBOGNATHUS 1 1 5 



Dorsal fin with usually 8 rays, occasionally 7, set slightly in front of ven- 

 trals, usually a little nearer muzzle than base of paudal; longest dorsal ray 

 1 to 1.2 in head; anal rays 8 (rarely 7) ; pectorals 1.1 to 1.4 in head; ven- 

 trals falling far short of vent in adults. Scales 5, 37-39, 4, large and 

 rounded, the exposed surfaces little deeper than long; lateral line com- 

 plete, and nearly straight except for a slight downward curve in front of 

 ventrals; scales before dorsal 13 to 16. 



This species is generally distributed throughout the state, 

 occurring in all our stream systems, including those of the Michigan 

 drainage, but most abundantly in those of southern Illinois. It is 

 essentially a river species — one of the few Illinois minnows occurring 

 in larger ratio in rivers than in creeks. It is most abundant in 

 rivers of the second class (coefficient, 2. 18), and next in creeks (1.91), 

 but we have also found it not very infrequent in the lakes and 

 ponds of the river bottoms ( . 43 ) . 



In general distribution it ranges from Delaware to Georgia and 

 Alabama, and from thence southwest to the Rio Grande, north to 

 the tributaries of the Missouri in the Dakotas, and to the Red River 

 of the North. In this state it is often found in deep and muddy 

 waters, and less frequently than most minnows in swift and gravelly 

 streams. It is one of the five Illinois species found most generally 

 over a mud bottom, its frequency coefficient being 1.68. It has 

 the long intestine, the simple pharyngeal teeth with a well-developed 

 grinding surface, and the few and short gill-fakers characteristic of 

 the mud-eating minnows, and its food corresponds to these struc- 

 tural peculiarities. According to our observations the intestine is 

 always filled with fine mud, containing only filamentous algse, 

 diatoms, and other vegetable forms likely to be found on a mud 

 bottom. It is frequently seen in large schools of from fifty to one 

 hundred in deep and quiet water, always lying nearer the bottom 

 than the top, or moving slowly along the bottom as it feeds. The 

 chisel-shaped lower jaw tipped with cartilage is probably used for 

 scraping up the mud and ooze. 



The sexual differences of this species are not striking, although 

 the spring males have the nuchal region somewhat swollen, and the 

 top and sides of the head beset with very minute tubercles. Fe- 

 males greatly distended with eggs have been taken by us early in 

 June. This minnow is not hardy, and is consequently an undesir- 

 able live bait. It is said by Dr. Bean to be much used for food. 



