222 FISHES OF ILLINOIS 



much like the mucin secreted by the vineyard snail, Helix pomatia. 

 The nest is built, by the exertions of the male alone, among the stems 

 of aquatic plants where there is some current.* It has two open- 

 ings, which are "as smooth and symmetrical as the hole leading into 

 a wren's nest, and not unlike it." The male induces the female to 

 enter the nest and lay her eggs, after which he enters and deposits 

 his milt. The holes in the nest are in the direction of the current, so 

 that a stream of water passes through it continually. The pugna- 

 cious male watches the nest and wards off all intruders. 



Key to the Genera of GASTEROSTEIDjE found ix Illinois 



a. Pubic bones firmly united, forming a lanceolate plate with a single strong 

 median keel; tail without keel, deeper than broad; dorsal spines 4 or 5, 



the spines in a right line, non-divergent Eucalia. 



aa. Pubic bones weak and feebly united to form an elongate plate with a 

 median longitudinal groove, on each side of which is a raised edge; tail 

 broader than deep, with lateral bony keel; dorsal spines S to 11, divergent 

 from right to left at various angles Pygosteus. 



Genus EUCALIA Jordan 

 (five-spined sticklebacks) 



Sticklebacks of typical form, feebly armed, the skin not mailed, and 

 the dorsal spines few (not more than S) and non-divergent; tail deeper 



than broad, without keel; pubic lmnes firmly united, forming a lam 



late plate with a single strong median carina. Fresh waters of N< rth 

 America; one species known. 



EUCALIA INCONSTANS (Kirtland) 



I BROOK STICKLEBACK) 



Kirtland. 1841, Bost. Journ. Nat Hist., 111. 27.^ (Gasterosteus). 

 | & (',.. 394 (Gasterosteus l ; M. V, "7; I & E. I. 744; X . 42 (inconstans and 

 pygma:a); J . 51 ; V .. 70 (Gasterosteus). F F . 1 6, 68; I. , 22 



Length 2\ inches; body rather deep and moderately compressed; 

 . audal peduni le rather stout and not keeled ; depth 3 . 8 to 4 . 4 ; greatesl 

 width about ; oi greatesl depth; depth of caudal peduncle 1.8 to 2.9 

 in its length, rotor (females and young) olivaceous, with faint lighter 

 mottlings and with many line dots of black-; upper part of sides and 

 caudal peduncle with about lo dark cross-bar-like bands more or less 

 confluenl in ring-like pattern; lower parts silvery; upper pari of cheek 



full description oi nest building of Gasterosteus cataphractus, see I K. Lord, 

 as quoted by Dr Jordan in "Guide to the Study of Fishes," Vol. [I., p 230. 



