FISHES OF COLORADO 93 



at Alamosa. That eels are found in the Rio Grande farther south is well estab- 

 lished, Girard in 1859 having described specimens from the Rio Grande under the 

 name of AnguiUa tyrannus. Judging from the remarkable distances covered by 

 migrating eels, the distance from the Colorado line to the mouth of the Rio Grande 

 would not be a prohibiting factor to the presence of the eel in Colorado. It is 

 here provisionally included in the Colorado fauna. 



Superorder ACANTHOPTERI 

 The Spiny-rayed Fishes 



Vertebrae just back of the head not fused; no Weberian apparatus; air 

 bladder in adults usually without a ductus pnemnaticus; scales usually ctenoid; 

 dorsal, pectorals, ventrals and usually the anal with spines. 



The majority of the species of this group, which is quite heterogeneous, are 

 marine fishes. Several large families of Spiny-rayed fishes are, however, com- 

 posed entirely of fresh-water species, notably the Ckhlidae in Central and South 

 America and the Centrarchidae in North America. Although represented in the 

 Mississippi VaUey by a large number of species, but four of this order occur native 

 in Colorado and all of these east of the Continental Divide. 



Order .Percoidea 



Family CENTRARCHIDAE 



The Sunfishes and Bass 



Spinous and soft dorsals united; scales ctenoid or cycloid; body strongly 



compressed and usually quite deep; mouth large, premaxillaries protractile; 



species carnivorous, known only from the fresh waters of North America. 



The species of this family form one of the most characteristic groups of North 

 American fishes, particularly since they are found only in the fresh waters of this 

 continent. Practically all of the thirty or more species of Centrarchids are caught 

 for food and two, the Black Bass, are among the best known of game fishes. A 

 single species of this family occurs native in Colorado, Lcpomis cyanellus Rafin- 

 esque, the Green Sunfish. Six other species have been introduced into the state 

 with varying success. 



Key to Centrarchidae Represented in Colorado 

 a. Anal spines V to VIII ; dorsal fin not twice the length of the anal fin. 



b. Dorsal spines V to VIII; anal and dorsal fins of about the same size and shape; eye blue 

 or brown Pomoxis Rafinesque, p. g4 



bb. Dorsal spines XI to XIII; dorsal fin longer than the anal; length of the base of^the anal 

 about 1 . 3 in the length of the base of the dorsal ; eye red . A mblopliks Rafinesque, p. 95 

 aa. Anal spines III; dorsal fin about twice the length of the anal fin. 



c. Dorsal fin without a deep indentation at the junction of the spinous and soft'portions; 

 spinous dorsal broadly joined to the soft dorsal; scales ctenoid or cycloid. 



