128 



within the Missouri basin. This is essentially a region covered with forests of 

 deciduous trees. It is true that some parts of it are prairie, but the soil contains 

 little or no alkali, and the small streams having their rise in it arc fairly clear 

 and pure. 



In the mountains at the headwaters of the various tril)utary streinns tliere is 

 an abundance of rainfall in summer and snow in winter; as a rule the mountains 

 were originally heavily timbered and the moisture was therefore conserved and 

 fed out slowly during the season of drought. This is still true in general, but the 

 reckless destruction of the forests in many places is having its effect upon the 

 streams. 



After leaving the mountains the tributaries of the Missouri, witii scnrcely an 

 exception, enter the broad treeless plain of the middle belt. Here the alkali soil 

 erodes easily, the current becomes slower, the bed broadens, the channel shifts 

 from year to year, and the water becomes warmer and often of the consistency of 

 thin soup. This is the character of all the larger streams as they pass through 

 this middle belt, and the character of the water is the same in all tlie smaller 

 streams which start in this belt. 



The Missouri Basin as a whole, however, is a country whose soils erode with 

 unusual ease and, after getting out of the mountains and upon the plain, few of 

 the streams are ever really clear The Missouri River is alwavs carrying vast 

 amounts of solid matter in suspension and justly deserves the name " Big Muddy." 

 The channels of the Missouri and all the larger tributaries are constantly chang- 

 ing and shifting the beds of the streams. 



THE FISHES OF THE MISSOURI RIVER 15ASIN. 



All this, of course, has its eflfects upon the tish fauna of this river system. 

 Each of the three belts ])ossesses a fish fauna differing very materially in the 

 aggregate from that of each of the other belts. 



The total number of species and subspecies of tisiies now recognized from the 

 entire Missouri basin is 143. These are distributed among 24 families and (58 

 genera. The families with large numbers of species are : 



The Cyprinidae, with 50 S{)ecies. 



The Percida', with 20 species. 



The Catostomidae, with 16 species. 



The (entrarchidiv, with 12 species. 



The Siluridw, with 10 species. 



