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BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Group PERCOIDEA. — The Pereh-like Fishes. 
A group of fishes of diverse habits and forms, but on the whole representing better than any other 
the typical Acantliopterygian fish. The group is incapable of concise definition, or, in general, of any 
definition 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 basses or Serrnnidx. 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 com- 
pressed laterally, and with the cheeks and opercles scaly; mouth variable, usually terminal and with 
lateral cleft, the teeth variable, but typically pointed, arranged in bands on the jaws, vomer, and 
palatine bones; gillrakers usually sharp, stoutish, armed with teeth; 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 4, a slit behind the fourth; gill- 
membranes free from the isthmus, and usually not connected with each other; pseudobranehise typically 
well developed; branchiostegals few, usually 6 or 7; no orbitosphenoid; 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 variously developed, but always with some spines in 
front, these typically stiff and pungent; anal fin typically short, usually with 3 spines, sometimes 
with a larger number, sometimes with none; caudal fin variable, usually lunate; pectoral fins well 
developed, inserted high; ventral fins always present, thoracic, separate, almost always with 1 spine 
and 5 rays; air-bladder usually present, without air-duct in the adult, simple, and generally adherent 
to the walls of the abdomen; stomach coecal, with pyloric appendages, the intestines short in most 
species, long in the herbivorous forms; vertebral column well developed, none of the vertebrae especi- 
ally modified, the number 10 — |- 14, except in certain extra-tropical and fresh-water forms, which retain 
the primitive higher numbers; shoulder-girdle normally developed, the post-temporal bifurcate, 
attached to the skull, but not coossified with it; none of the epipleural bones attached to the center of 
the vertebrae; coracoids normal, the hypercoracoid always with a median foramen, the basal bones 
of the pectoral (actinosts or pterygials) normally developed, 3 or 4 in number, hourglass-shaped, 
longer than broad; premaxillary forming the border of mouth, usually protractile; bones of the man- 
dible distinct. Species very numerous, found in all seas except those of the Arctic regions. Many 
species inhabit fresh waters, especially in North America and Europe. These fresh-water forms are 
apparently nearer the primitive stock than the marine species are. The Elassomidx, Centrarchidx, 
and Perch ff are the most primitive, and apparently form, with the Percopsidx and Aphredoderidx, an 
almost continuous series. This series, however, we are compelled to break in a linear arrangement 
for the purpose of bringing in other series of transitional forms, which culminate in Berycoids and the 
Scombroids. 
KEY TO FAMILIES OF PERCOIDEA. 
a. Maxillary not sheathed by the preorbital or only partially covered by the edge of the latter; ventral with its accessory 
scale very small or wanting; opercle usually ending in a spine. 
b. Precaudal vertebra with transverse processes from the third or fourth to the last; ribs all but the last lto 4, sessile, 
inserted on the centra behind the transverse processes; pseudobranehise large; dorsal spines about 10. 
Kuhliidx, p. 207 
lib. Precaudal vertebrse anteriorly without transverse processes; all or most of the ribs inserted on the transverse 
processes when these are developed. 
c. Anal spines 2, rarely 3; vertebra 24 or 25; dorsal fin divided Apogoniehthyidse, p. 209 
cc. Anal spines 3, never 2 nor 1; dorsal fin continuous or divided; vertebrse 24 to 35. 
d. Anal fin shorter than dorsal; head not everywhere covered with rough scales; postocular part of head not short- 
ened Scrranidir , p. -219 
dd. Anal fin scarcely shorter than dorsal and similar to it; head and body everywhere covered with rough scales; 
body deep, compressed Priacanthidx, p. 227 
aa. Maxillary slipping for most of its length under the edge of the preorbital, which forms a more or less distinct sheath; 
vent.rals with an accessory scale; opercle without spines. 
e. Carnivorous species; teeth in jaws not all incisor-like. 
/. Spines of premaxillary not greatly produced, not extending backward to the occiput; mouth moderately 
protractile. 
