CATOSTOMUS — FINE-SCALED SUCKERS 87 



westward to Minnesota and Kansas, north to the Lake of the 

 Woods, and south to Arkansas. It is especially abundant in 

 swift and rapid streams, and is rarely found in muddy water. 

 Its avoidance of muddy situations is illustrated especially by its 

 distribution in Illinois, not a single collection of this species 

 having been made by us from the persistently turbid water of 

 the lower Illinoisan glaciation. It is rare in the southern third 

 of the state, and was taken by us but once from any locality 

 of extreme southern Ihinois. It has occurred in our collections 

 most abundantly in the headwaters and smaller tributaries of 

 the Illinois, the Kaskaskia, the Embarras, and the Big Ver- 

 milion, in the northern and eastern parts of the state. 



The most striking peculiarities of this fish are related to its 

 haunts and feeding habits. The large bony head and the un- 

 usually developed pectoral fins, together with the full lips and 

 the papillose mouth, are all related to the fact that it seeks its 

 food in the more rapid parts of streams, pushing about the stones 

 upon the bottoms and sucking up the ooze and sUme thus ex- 

 posed, together with the insect larvae upon which it mainly, 

 depends for food. The slender body, the large pectoral fins, 

 and the comparatively high coloration of this species give it 

 the aspect of a darter among the suckers, and its active habit 

 and the peculiar character of its food resources is another point 

 of affinity with that interesting group. It has also, like the 

 darters, the habit of resting quietly on the bottom, supported 

 by its paired fins, where its coarsely mottled colors serve well 

 to conceal it among the surrounding stones. 



Proportionately to the number of collections made by us, 

 this species was about three times as abundant in central Illinois 

 as in southern, and three and a half times so in northern Illinois 

 as in central. It was much commonest in the smaller rivers and 

 about half as abundant in creeks, although not wholly wanting 

 in either the larger rivers or in the glaciated lakes of northeastern 

 Illinois. It was not taken by us at all off really muddy bottoms. 



Widel}^ different as are the food and feeding habits of this 

 species and those of the common sucker, its nearest ally in our 

 waters, their alimentary structures are not remarkably unlike. 

 The pharyngeals of the present species are somewhat lighter, the 

 pharyngeal teeth more slender and more prominently hooked, 

 and the gill-rakers somewhat stouter, thus affording a better 

 apparatus for the retention of the relatively large insect larvae 

 upon which this species chiefly feeds. It is, in short, a molluscan 



