48 FISHES OF ILLINOIS 



of about 3 pieces, forming lateral margin of upper jaw; teeth usually small 

 or wanting, variously arranged; air-bladder large, with open duct. 



Species numerous (about 150 known), abundant and widely 

 distributed in all seas, usually swimming in immense schools. 

 Many species ascend fresh waters in spring to spawn and a few 

 are permanent residents in fresh water. Two genera are found 

 in streams tributary to the Atlantic and the Gulf and in the 

 Mississippi Valley. 



Key to the Genera of CLUPEID^ found in Illinois 



a. Premaxillaries meeting- at a larg-e angle, so that the tip of the upper jaw does 



not appear to be notched; cheeks longer than deep; teeth feeble. ..Pomolobus. 



aa. Premaxillaries meeting in front at a very acute angle, so that the emarginate 



front of the upper jaw receives the slender tip of the lower; fore part of 



cheeks very deep, deeper than long; jaws toothless Alosa 



Genus POMOLOBUS Eafinesque 



ALEWIVES 



Body rather elongate, more or less compressed; belly sharp-edged, 

 strongly serrated before and behind ventrals; mouth terminal, oblique; jaws 

 about equal, the upper somewhat notched at tip; mandible shutting "s\dthin 

 maxillaries; teeth feeble, variously placed; dorsal short, nearly median, its 

 posterior ray not prolonged in a filament; scales thin, cycloid. Species 

 numerous, mostly anadromous, inhabiting both northern and tropical seas; 

 one species found in fresh waters of ihe Mississippi Valley. 



POMOLOBUS CHRYSOCHLORIS Eafinesque 



GOLDEN shad; SKIPJACK; BLUE HERRING 



Rafinesque, 1820, Ichth. Oh., 39. 



J. & G., 266 (Clupea); M. V., 73 (Clupea); J. & E., I, 425; N., 44 (misspelled); J., 

 55; F., 73 (Clupea); P. P., IL 7, 439; K, 20. 



Length 15 inches; body elongate, com- 

 pressed, greatest width somewhat less than 

 23^ in dep^h in adults; depth 3.6 to 4.3; 

 depth caudal peduncle 1.4 to 1.6 in its 

 length. Color silvery to greenish with bluish 

 and golden reflections; back light olive-gray 

 '^^ J^ with strong bluish luster; sides light olive- 



green, shading to silvery white, with golden 

 luster; belly opaque milk-white; no dark 

 P(j(. 13 spot behind opercle. Head pointed, 3.7 to 



4 in length; width head 2.3 to 2.6 in its 

 length; interorbital space 5.8 ^o 6.3 in head, less than eye; eye 4.5 to 5.9 in 

 head; adipose eyehd present; nose 4.3 to 5.2 in head, mouth large, terminal, 



