April, 1910. Fishes of Chicago — Meek and Hildebrand. 301 



Order Acaiithopteri. 



The Spiny-rayed Fishes. 



Skeleton bony; the anterior vertebrae 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. G aster osteicke, 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. Percopsida, 303 



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

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



Atherinida, 304 

 aa. Ventral fins thoracic. 



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

 throat. Aphredoderida, 305 



dd. Ventral rays of one spine and 3 to 5 soft ravs; 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 % length of longest soft ray. 



CentrarchidfB 306 

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

 confluent the longest dorsal spine is longer than longest soft ray. 

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



ii. Anal fin with 3 spines. SerranidcB, 332 



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

 teeth. Scicenida, 334 



