224 FISHES OF ILLINOIS 



Genus PYGOSTEUS Brevoort 

 (nine-spined sticklebacks) 



Dorsal spines 9 to 11, divergent from right to left at various angles ; 

 tail broader than deep, with a lateral bony keel; pubic bones weak and 

 feebly united, forming an elongate plate with a median longitudinal 

 groove, on each side of which is a raised edge*; characters otherwise as 

 in Eucalia. Species two, in the waters of northern regions, one of them 

 native in China; a single species, cosmopolitan in distribution, found in 

 the waters of Illinois. 



PYGOSTEUS PUNGITIUS (Linn^us) 



(nine-spined stickleback) 



Linnseus, 17 58, Syst. Nat., Ed. X, 296 (Gasterosteus). 



G., I, 6 (Gasterosteus); J. & G., 393 (Gasterosteus); M. V., 97; J. & E., I, 745; X., 

 42 (nebulosus) ; J., 51 (occidentalis var. nebulosus) ; F. F., I. 6, 69. 



Length 3 inches; body quite slender, considerably compressed, the 

 caudal peduncle very long, slender and tapering, broader than deep, and 

 with lateral bony keel; depth 5 . 1 to 5 . 6 ; greatest width about | of great- 

 est depth; depth of caudal peduncle 4.3 to 6.2 in its length. "Color 

 olivaceous above, profusely punctulate, irregularly barred with darker; 

 silvery below" (J. & E.). Head 3 .3 to 3 . 7 ; width 2.4 to 3; interorbital 

 space 4 . 5 to 5 . 1 in head ; eye 3 ; nose i .3 to 3.8; mouth somewhat less 

 oblique than in the last species, the maxillary nearly to orbit, 3 .i to 4.4 

 in head. Dorsal IX (or X), 9 or 10, the spines promiscuously divergent 

 to right and left at various angles; caudal scarcelv lunate; anal rather 

 low, the spine nearly as long as anterior ravs; ventrals with a long finelv 

 serrated spine, which is less than 3 in head; pectorals 1 . 7 to 1 . 9 in head; 

 post-pectoral plate well developed; thoracic processes prominent, form- 

 ing a U-shaped figure; pubic bones thin and feebly united, lanceolate, 

 with a median groove between two raised edges. Skin naked except for 

 small bony plates along bases of dorsal and anal and on caudal keel. 



This little species has been taken by us but once, and then from 

 the lower Calumet River and from Lake Michigan near the mouth of 

 that stream. It inhabits both fresh and brackish water, and is 

 found throughout northern Europe, and in North America as far 

 southward as the Great Lake region. It is thus a strictly northern 

 species. 



Our only hint of its food was given us by the examination of two 

 specimens which had fed wholly on the larvae of gnats (Chironomiis 

 and Simulium) and on various Entomostraca. 



*Not verified for P. sinensis, of China. 



