114 TELEOSTEI : — ACANTHOPTERI. — XX. 



minute or obsolete ; preopercle entire or nearly so ; preorbital deep, 

 not sheathing the maxillary ; gill membranes separate, free from 

 isthmus ; pseudobranchiae small, concealed. B. usually 6 ; lower 

 pharyngeals separate ; scales usually large ; lateral line present. 

 Dorsal continuous, with 6 to 13 spines; anal spines 3 to 8. Ver- 

 tebrae about 30. Intestines short, with a few caeca. Sexes similar, 

 but the changes in form due to age often considerable. Genera 10 ; 

 species about 25 ; carnivorous fishes especially characteristic of the 

 Mississippi Valley, ■ — ■ all but one (Archoplites interruptus of Cal.) 

 confined to the waters of the E. U. S. Some species build nests, 

 and all are voracious and gamy. 



a. Dorsal fin scarcely larger than anal ; gill rakers very long and slender. 



b. Spinous dorsal longer than soft, its spines 12 ; anal spines about 8. 



Centraechus, 149. 



hb. Spinous dorsal shorter than soft, with 6 to 8 spines; anal spines 6. 



POMOXIS, 150. 

 aa. Dorsal fin much larger than anal ; gill rakers shorter. 



c. Body comparatively short and deep, the depth usually more than 2 

 the length; dorsal fin not deeply divided. 

 d. Tongue and pterygoids with teeth; mouth large (the maxillary 

 reaching past middle of eye). 

 e. Scales ctenoid; caudal concave behind. 

 /. Opercle emarginate behind; anal spines usually 6; branchios- 



tegals 6 Ameloplites, 151. 



ff. Opercle ending in a black convex process or flap ; anal spines 3. 



Ch^nobryttus, 152. 

 ee. Scales cycloid ; caudal convex. . . . Acantharchus, 153. 

 dd. Tongue and pterygoids toothless ; mouth small (the maxillary barely 

 to middle of eye). 



g. Caudal convex ; opercle emarginate, without flap. 

 A. Dorsal fin continuous, normally with 9 spines; anal nor- 

 mally with 3 spines Enneacakthus, 154. 



hh. Dorsal fin angulated, some of the median spines elevated ; 

 dorsal spines 10; anal 3. . . . Mesogosistius, 155. 

 gg. Caudal margin concave ; opercle prolonged behind in a con- 

 vex process or flap which is always black ; dorsal spines 



normally 10; anal 3 Lepomis, 156. 



CO. Body comparatively elongate, the depth in adult about J the length; 

 D. low, deeply emarginate, with 10 spines; mouth large; C. lunate. 



MiCEOPTERUS, 157. 



149. CBNTRARCHUS Cuv. & Val. {Kivrpov, spine ; 

 dpxos, anus.) 

 297. C. macropterus Lacepede. Body ovate ; fins hio-h. Green, 

 with rows of dark brown spots along sides ; fins reticulated ; young 

 ■with a black ocellus on D. behind. Head 3\ ; depth 2. Scales 

 5-44-14. D. XI or XII, 12. A. VII or VIII, 15. L. 6. N. C. 

 to 111., and S., in lowland streams. (/laKpos, long ; irrcaov, fin.) 



