April, igio. Fishes of Chicago — Meek axd Hildebraxd. 301 



Order Acanthopferi. 



The Spinv-rayed Fishes. 



Skeleton bony; the anterior vertebras not modified; anterior rays 

 of dorsal and anal fin usually spinous ; opercular apparatus complete ; 

 border of the mouth formed by premaxillaries ; maxillary present, 

 and without teeth; ventral fins usually thoracic and usually formed of 

 I spine and 5 soft rays; air bladder present, without duct in the adult; 

 scales when present usually ctenoid. 



a. Ventral fins abdominal. 



b. Dorsal fin single preceded by 4 or more spines, not connected 

 by a membrane; no adipose fin. Gasterosteidce, 302 



bb. Dorsal fins 2 ; spines connected by a membrane. 



c. Anterior dorsal composed of one weak spine and soft rays; 

 the second dorsal adipose. Percopsidcs, 303 



cc. Anterior dorsal composed of 3 to 8 slender spines connected 



by a membrane ; the posterior fin composed of soft rays. 



AtherinidcE, 304 

 aa. Ventral fins thoracic. 



d. Ventral rays of one spine and 6 or 7 soft rays; vent near the 

 throat. AphredoderidcB, 305 



dd. Ventral rays of one spine and 3 to 5 soft rays; vent near anal 

 fin. 



e. Chin without a barbel; dorsal and anal fins of less than 30 soft 

 rays; caudal fin homocercal. 



f. Body more or less covered by typical scales. 



g. Lateral line not extending on rays of caudal fin ; jaws with 

 teeth. 



h. Dorsal fin with spinous portion confluent with soft portion, or 

 separated by a deep notch in which case the longest dorsal 

 spine is but little more than X length of longest soft ray. 



Centrarchidce 306 

 hh. Dorsal fins with spinous and soft portions separate, or if slightly 

 confluent the longest dorsal spine is longer than longest soft ra\ . 

 i. Anal fin with i or 2 spines. Percidce, 317 



ii. Anal fin with 3 spines. SerranidcJB, 332 



gg. Lateral line extending on rays of caudal fin; jaws without 

 teeth. ScicF) i idee . 334 



