EXPLANATION OF TABLES AND MAPS. 



In place of the names of species, the corresponding numbers of Jordan and Ever- 

 inann'9 "Synopsis of North American Fishes" have been used in the construction of 

 the tables, as follows: — 



1417. Percina caprodes (Raf. ). 



1418. Hadropterua phoxocepholus (Nelson). 

 1421. Hadropterus aspro (Cope & Jordan). 

 14,36. Cottogaster shumardi (Gir.). 



1443. Diplesion blennioides (Raf.). 



1446. Boleosoma nigrum (Raf.). 



1448. Boleosoma camurum Forbes. 



1450. Ammocrypta pellucida (Baird). 



1461. Etheostoma zonale (Cope). 



1474. Etheostoma jessise (Jordan & Brayton). 



1477. Etheostoma cozruleum Storer. 



1490. Etheostoma flabellare Raf. 



1494. Boleichthys fusiformis (Gir.). 



Table I. shows, under each species number, first, the number of collections of the 

 species used in this study; second, the coefficients of the association of the species with 

 each of the others of the group of thirteen represented by this table, these coefficients 

 being arranged in order of magnitude from above downward; and, third, the totals 

 and the averages for each column. The species columns are arranged in the order of 

 their average coefficients. At the bottom of the table is the sum of the totals for the 

 species and the general average of their average coefficients, the last being the gen- 

 eral associative coefficient for the entire group. 



In Table II. the species numbers are placed in like order at the top and at the side 

 of the table, and the coefficient of any two species will be found at the point of inter- 

 section of the column for one with the line for the other. The upper right half of 

 this table is the reversed duplicate of the lower left half, inserted for convenience in 

 following a series of coefficients. 



Table III. is constructed like Table II., but with totals and averages added, as in 

 Table I. It contains the coefficients of mutual association of the last three species of 

 Table I., which are distinguished by the lowest average coefficients of the whole se- 

 ries of thirteen. 



Table IV. is constructed like Table III. It contains the coefficients of mutual asso- 

 ciation of the "typical darters" — the first six of Table I. distinguished by their high 

 average coefficients. 



Table V. contains the coefficients of mutual association of the seven species which 

 have occurred least frequently in my collections. 



Table VI. is intended to represent the relations of preference and avoidance of 

 the various species with reference to kinds of bodies of water, to current movements, 

 and to character of bottom, so far as these are determinable from our data. AVhere 

 the ratios do not amount to 100 per cent., the difference is due to the omission of 

 miscellaneous minor data. 



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