Order xi. Acanthopteri. 



The Spiny-rayed Fishes. 



Anterior vertebras unmodified; one or more fins with spines; 

 ventral fins usually placed anterior, normally attached to the pelvis 

 and typically with one spine and five soft rays, sometimes fewer or 

 wanting, sometimes without spine or with many rays, or otherwise 

 modified; gill openings normal, large; scales usually ctenoid. 



KEY TO THE FAMILIES OF ACANTHOPTERI. 



a. Eyes symmetrical, one or more fins with spines; page 



dorsal fin short, its combined spines and rays 

 less than 30. 

 b. Lateral line present; ventral fins not close 

 together, the outer rays the longer, 

 c. Dorsal fins 2, well separated, the first of 3 to 

 8 spines; no well developed lateral line; 

 some scales often with rudimentary mucus 

 tubes. 



d. Anal fin with one weak spine ; dorsal spines 

 3 to 8, flexible; stomach not gizzard-like; 



alimentary canal short; species carnivorous. . Athcrinidce 165 

 dd. Anal spines 2 or 3 ; dorsal with 4 stiff 

 spines, the last one being much shorter 

 than the others; stomach gizzard -like; 



alimentar}'- canal long Mugilidce 185 



cc. Dorsal fin single, or, if 2 fins, the spinous 

 slightly separated from the soft portion; 

 lateral line more or less developed. 



e. Lateral line not interrupted; nostrils 2 on 

 each side. 



f. Maxillary not sheathed by the preorbital, 

 or only partially covered by its edge ; ven- 

 tral with its accessory scale very small, or 

 wanting, 

 g. Anal spines 3 to 9 ; dorsal fins confluent ; 



body usually much compressed Centrarchidoe 180 



gg. Anal spines 1 or 2; dorsal fins 2, slightly 



separate; body but slightly compressed Percidee 196 



ff. Maxillary slipping for most of its length 

 under the edge of the preorbital, which 



164 



