CHAPTER XVIII 

 PERCOIDEA, OR PERCH-LIKE FISHES 



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ERCOID Fishes. We may now take up the long 

 series of the Percoidea, the fishes built on the type 

 of the perch or bass. This is a group of fishes of 

 diverse habits and forms, but on the whole representing better 

 than any other the typical Acanthopterygian fish. The group 

 is incapable of concise definition, or, in general, of any defini- 

 tion at all; still, most of its members are definitely related 

 to each other and bear in one way or another a resemblance 

 to the typical form, the perch, or more strictly to its marine 

 relatives, the sea-bass, or Serranidaz. The following analysis 

 gives most of the common characters of the group: 



Body usually oblong, covered with scales, which are 

 typically ctenoid, not smooth nor spinous, and of moderate 

 size. Lateral line typically present and concurrent with 

 the back. Head usually compressed laterally and with the 

 cheeks and opercles scaly. Mouth various, usually terminal 

 and with lateral cleft; the teeth various, but typically pointed, 

 arranged in bands on the jaws, and in several families on the 

 vomer and palatine bones also, as well as on the pharyngeals; 

 gill-rakers usually sharp, stoutish, armed with teeth, but some- 

 times short or feeble ; lower pharyngeals almost always separate, 

 usually armed with cardiform teeth; third upper pharyngeal 

 moderately enlarged, elongate, not articulated to the cranium, 

 the fourth typically present ; gills four, a slit behind the fourth ; 

 gill membranes free from the isthmus, and usually not con- 

 nected with each other; pseudobranchiae typically well 

 developed. Branchiostegals few, usually six or seven. No 

 bony stay connecting the suborbital chain to the preopercle. 

 Opercular bones all well developed, normal in position; the 

 preopercle typically serrate. No cranial spines. Dorsal fin 



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