102 FISHES OF ILLINOIS 



had been uniformly distributed. From the entry in the third col- 

 umn it will be seen that in small rivers the abundance of Cam- 

 postoma anomalum was a little more than 2i times as great as if 

 the species had been uniformly distributed; and from the fourth 

 column, that in creeks it was a little more than 3} times as abun- 

 dant. The number of its occurrences in lowland lakes was but . 05 

 of the normal average, and in upland lakes the species has not been 

 taken by us at all. 



The seventh and tenth columns of these figures give the num- 

 bers of collections for each species concerning which data were 

 recorded available for computing their relative frequencies in rapid 

 and quiet waters, and on clean and soft bottoms. From the figures 

 in the last six columns of the table we learn, concerning Canipos- 

 toma, that 65 collections give us a coefficient of 1 . 7 for a rapid cur- 

 rent as compared with .59 for quiet water, equal frequency in the 

 two situations being, as before, represented by 1. The strong pref- 

 erence of the species for a clean bottom over one of mud is shown 

 by the last two numbers, applying to 105 collections, the tw^o 

 coefficients being respectively 3.26 for a clean bottom and .31 for 

 one of mud. 



In Tables II. to V., relating to minnows and the environment, 

 the species most characteristic of each situation are brought to- 

 gether in lists arranged in the order of the size of their coefficients of 

 frequency. The remaining lists refer to peculiarities of territorial 

 distribution within the state. 



The following keys and descriptions of Cyprinidcs have been 

 designed for use with a minimum of attention to obscure charac- 

 ters and to those difficult of access. However, it will be necessary 

 in all cases for beginners in ichthyology to ascertain by dissection 

 whether their specimen belongs to the long- or the short-intestined 

 class of minnows (see key to genera of CyprinidcE). It is possible, 

 however, to dispense entirely with the use of dental characters in 

 the indentification of minnows, and our keys have been construct- 

 ed with that fact in view; although, for the purpose of complete- 

 ness and for the aid of those who may wish to carry their studies 

 further than the simplest artificial key will take them, we have in 

 every case included a reference to the number and form of the 

 pharyngeal teeth.* 



*In Illinois Cyprinidce the main row of teeth on each pharyngeal bone con- 

 tains 4 or 5 teeth; inside of this main row is a so-called "lesser row," which 

 m.ay contain 1 or 2 teeth, or be unrepresented altogether, in the latter case being 

 designated "0" in the formula. For example, "teeth 2, 4-4, 2" means 4 teeth in 



