KEY TO GENERA— P^RCID^. 87 



Family : PERCID.E. 



Key to Genera. 



PseudobmnchiEe well developed ; preopercle serrate ; branchiostegals 7 ; no anal 

 papilla. 



B. Canine teeth on jaws and palatines; body elongate: ventral fins well sepa- 



rated. — Stizostedion. 



BB. Canine teeth none ; body oblong, ventral fins near together. — Perca. 



Pseudobranchiae imperfect or wanting ; preopercle entire or nearly so ; branchios- 

 tegals 6 ; anal papilla usually present. 



C. Parietal region of skull depressed, not strongly convex in transverse section, 



—shaped in section. 

 D. Cranium broad between the eyes, snout conic, projecting pig-like beyond 



the inferior mouth. — Percina. 



DD. Cranium not broad between the eyes, snout not much proj.cting. 



E. Body not hyaline nor extremely elongate, its surface almost en- 

 tirely covered with scales. 

 F. Premaxillaries not protractile, the skin of the premaxillary 

 continuous in the middle with that of the forehead with no 

 cross groove between. — Hadroptertts. 



FF. Premaxillaries protractile (in Cottogaster shumardi a narrow, 

 connecting f reuum sometimes crosses from the premaxillary 

 to the forehead). 



G. Anal spines 2, both well developed, the first usually the 

 longer. 

 H. Mid-line of belly naked or covered by caducous 

 shields ; gill membranes scarcely conne ted — 

 Cottogaster. 

 HH. Belly covered' with ordinary scales ; gill mem- 

 branes broadly connected. — Diplesion. 

 GG. Anal spine single, obscure ; anal fin small, much shorter 

 than soft dorsal. — Boleosoma. 

 EE- Body extremely elongate, hyaline, subterete, the belly mostly 

 naked. 



I. Premaxillaries not protractile ; dorsal spines 12 or 13.— 



Crystallaria. 



II. Premaxillaries protractile ; dorsal spines 9 to 11. — 



Ammocrypta. 

 CC. Parietal region of skull not depressed, more or less strongly convex in cross- 

 section, n -shaped; premaxillaries never protractile; belly covered with 

 ordinary scales. 

 J. Lateral line straight ; body rather robust.— Etheostoma. 



JJ. Lateral line with a slight arch running high anteriorly ; body slender. — 



Boleichthys. 



